Kiriyenko refused to say how polonium was produced, but said nuclear reactors like the Russian RMBK or the Canadian CANDU were needed to make it.

"In Russia all nuclear reactors, including those used for research, are government property tightly controlled by federal authorities," he said.

Limarev then produced an e-mail which he said had come from Scaramella on the day of the sushi bar meeting, referring to Litvinenko 'interrupting relations' with Berezovsky on the advice of the US and Britain. Limarev refused to show The Mail on Sunday the whole of the email, which was written in very poor English.

But he said that Scaramella told him that Litvinenko had been warned by agents.

It is the first suggestion of the involvement of Western intelligence agents in the intrigue and the most direct hint that Litvinenko could have been targeted because of his ties to Berezovsky's circle.

The tycoon claimed political asylum to Britain in 2001 after being accused of business irregularities, and is seen as the unofficial leader of the band of Russian dissidents who live in London.

Limarev produced the extract from the email in an exclusive interview with The Mail on Sunday yesterday morning at a location near his safe house in the French Alps.

Limarev also responded to claims that he sent information to Scaramella which caused him to set up the sushi lunch. He is said to have warned that both Scaramella and Litvinenko were at risk of being killed by renegade members of Spetsnaz, the Russian equivalent of the SAS, because of their criticism of Russian President Vladimir Putin.

Spetsnaz, an elite unit attached to the intelligence section of the army, specialises in close quarters hand-to-hand combat.

Limarev, 41, who admits to links with Russian intelligence agencies but denies reports that he was ever a listed KGB officer, fled Russia seven years ago after falling out with influential politicians and businessmen in Moscow.

Chain-smoking nervously, he denied being the sole source of the information which Scaramella used as a pretext to arrange the lunch. 'I was just one of many sources for that information,' he said. 'Scaramella used me to distract attention from himself and because he was scared.'

Astonishingly, Limarev also claimed that he was the victim of a suspicious robbery in Rome on the day that news of Litvinenko's condition broke. While he was in Italy, a bag containing Limarev's personal papers and house keys were stolen. Three days later the keys were used to try to gain entry to his safe house 500 miles away - but the locks had already been changed.

He said: 'What worries me is that very few people knew I was in Italy and knew where I was staying. They tried to enter my house very professionally. The tyres on my car had also been let down.'

Limarev says he first encountered Litvinenko in 2001, contacting him to ask him to speak to Berezovsky about possible business deals.

Litvinenko then introduced Limarev to Scaramella, who invited him to help with his work on an Italian Parliamentary investigation - the Mitrokhin Commissiion - into KGB activity in the country during the Cold War. Limarev says he stopped working for Scaramella in 2005 after he became concerned about the Commission's activities.

He said: 'I don't know who pays Scaramella. My guess is that his money comes from a number of sources - very likely US and Italian, but I really don't know if he gets anything from Russia.

'Scaramella seems to be obsessed with nuclear topics,' he added, referring to Scaramella's work for a mysterious outfit called the Environmental Crime Prevention Program, which apparently uses satellites to track nuclear waste.

'But I don't think Mario was Litvinenko's killer. Maybe the killers contaminated him a little at the same time as they poisoned Alex to implicate him, maybe he was contaminated by accident.

'I also think the two Russians who met Litvinenko later that afternoon were used: the killers will have followed him for weeks, and then decided that this was the perfect day to do the hit.'

Limarev added that he was called by Alex Goldfarb, who has acted as a spokesman for Litvinenko's family during the affair, last Sunday when his picture appeared in The Mail on Sunday over revelations about the mysterious robbery in Rome.

Limarev said that Mr Goldfarb told him: 'Welcome to the club,' - the 'club' being the small group of Russians involved in the drama.

Limarev, whose father was a senior KGB officer, says he retains good sources in the Russian intelligence services.

"We know how the FSB operates abroad and, based on the circumstances behind the death of Mr Litvinenko, the FSB has to be the prime suspect," a source said on Monday.

The involvement of a former FSB officer made it easier to lure Mr Litvinenko to meetings at various locations and to distance its bosses in the Kremlin from being directly implicated in the plot.

Intelligence officials say that only officials such as FSB agents would have been able to obtain sufficent amounts of polonium-210, the radioactive substance used to fatally poison Litvinenko only weeks after he was given British citizenship.

MI5 and MI6 are working closely with Scotland Yard on the investigation. A senior police source told The Times yesterday that the method used to kill the 43-year-old dissident was intended to send a message to his friends and allies.

"It's such a bad way to die, they must have known," the source said. "The sheer organisation involved could only have been managed by professionals adept at operating internationally."

Nine Scotland Yard detectives are in Moscow, and they are determined to question a number of well-connected businessmen, despite a warning yesterday from Sergei Lavrov, the Russian Foreign Minister, that speculation over the poisoning is straining relations between the two governments.

"It's unacceptable that a campaign should be whipped up with the participation of officials. This is of course harming our relations," Mr Lavrov said during a visit to Brussels.

He said that he had spoken to Margaret Beckett, the Foreign Secretary, "about the necessity to avoid any kind of politicisation of this matter, this tragedy".

British ministers insist that diplomatic sensitivities will not be allowed to obstruct the scope of the Yard investigation.

John Reid, the Home Secretary, who was also in Brussels briefing his European counterparts on the Litvinenko affair, said: "The police will follow the evidence wherever it goes."

The main figure that the British counter-terror team want to question is Andrei Lugovoy, a former FSB agent. He made three visits to London in the fortnight before Mr Litvinenko fell ill and met him four times at various restaurants and bars.

Lugovoy, who is a successful entrepreneur, was briefly imprisoned in Moscow after he left the FSB. After his release his business career thrived and his company is reported to be worth more than GBP100 million.

Two hotels in London in which he stayed had traces of polonium-210, as did a British Airways aircraft that Mr Lugovoy travelled on. He was among three Russians who last met Litvinenko at the Millennium Hotel on November 1, the day that he fell ill.

Last night Lugovoy told The Times that he and two business associates, Dmitri Kovtun and Vyacheslav Sokolenko, were ready to meet detectives.

The men have all denied involvement in any poison plot.

The judgment by British Intelligence has been strengthened by the knowledge that the FSB has legislative approval for eliminating terrorists and enemies of the state abroad, after the passing of a controversial anti-terrorism law in the summer.

According to the paper, four Israeli jewelers and diamond dealers convicted of illicit diamond smuggling in Russia are currently held in a Moscow prison. The authors of the story insist that the four men are effectively held hostage as Russia, seeking extradition of Leonid Nevzlin, refuses to allow them to serve their terms at home, in violation of diplomatic accords signed by the two countries.

The wrongdoings attributed to the Israeli nationals were decriminalized after the four were convicted. In talks with Israeli officials and families of the convicts the Russian officials reportedly hinted at the possibility of "the exchange".

Moscow and Tel-Aviv signed the extradition agreement two years ago. Russia has already used it once when Israel extradited a Russian-Israeli suspect on condition that if convicted he would serve his prison term in Israel. Russia honored its commitments under the treaty.

But ever since the Israeli jewelers were found guilty in Moscow two years ago numerous requests made by Israel to let them return home have been flatly rejected by Russia. Even personal requests made by top Israeli ministers were ignored, Yedioth Ahronoth reported.

One of the convicts has recently wrote a letter to his relatives where he claimed that in October 2005 he and his inmates were visited in their cell by an unidentified man who informed them that their task was to bring Nevzlin back to Russia and assured them that if they agreed to help Russian law enforcers they would be discharged from prison; if not they would have to serve their entire terms in Russia.

The NEWSru Israel website asked Leonid Nevzlin who currently lives in Israel to comment on Yedioth Ahronoth's report. "I have heard that those convicts were warned that if Israel refused to extradite Nevzlin they could abandon hope for early release or transfer to an Israeli prison. I also know that my extradition has many times been discussed at meetings between top Israeli and Russian foreign ministry officials but those conversations were never officially recorded," the entrepreneur said.

Nevzlin also pointed out to an inaccuracy in Yedioth Ahronoth's report. "In truth, there is no permanent extradition pact between Russia and Israel saying that criminals shall serve their sentences at home. Such an accord was achieved once, on the Zhuravlyov case (Multiple murder suspect Andrei Zhuravlyov, aka Terrazini, was extradited to Russia in 2002, after the court said he had obtained Israeli citizenship unlawfully). As to the jewelers' case a separate agreement was drawn up," Nevzlin said.

Nevzlin said he had no reason to doubt the facts unearthed by Yedioth Ahronoth. "I view [Russia's actions] as a hostage-taking in spite of the fact that those people had been arrested before I moved to Israel. In fact, what we deal with here is blackmail where innocent Israeli are being used as bargaining chips," Nevzlin said.

"In case the status solution is not acceptable to both sides - both Belgrade and Pristina - the Russian side will use its veto power," Alekseyev was quoted as saying.

There was no immediate confirmation of the comments by the Russian Embassy in Belgrade. Alexeyev spoke in Russian with a Serbian translation by B92, The Associated Press reports.

Kosovo is formally part of Serbia, but its majority ethnic Albanians overwhelmingly support independence for the province - the demand that Serbia has vowed never to accept.

International talks aimed at defining a solution for Kosovo started early this year under U.N. mediation, but so far have produced no result because the two sides remain entrenched in their positions.

The Kosovo issue is believed to be the last potential flashpoint in the Balkans.

Following lack of progress in the talks, U.N. envoy Martti Ahtisaari has started working on a proposal for the province. The draft solution is expected to be presented to major world powers of the so-called Contact Group, and the two sides in the talks early next year.

The future solution also needs approval at the U.N. Security Council - where Russia has veto power - before it can take effect.

Serbian officials repeatedly have said they count on Russia's veto in the Security Council to prevent Kosovo independence, but Alexeyev comments to B92 mark the first time a Russian official confirmed such a possibility. There was no immediate comment from Moscow.

Russia in the past has urged both sides to find a negotiated settlement and warned against one-sided solutions. Moscow fears that Kosovo independence could set a precedent for Russian-backed separatist regions in the former Soviet Union.

Kosovo became an international protectorate in 1999, after NATO intervened in the province to stop a Serbian crackdown against ethnic Albanian separatists.

Russia is considered to be a traditional Serbian ally. Both countries share strong cultural, historic and religious ties.

Russian Orthodox officials accuse Catholic Church representatives of poaching in the traditionally Orthodox regions of Russia and some other ex-Soviet republics. The Vatican has rejected the proselytizing allegations, saying it is only ministering to Russia's tiny Catholic community - about 600,000 people in a country of 144 million.

"I hope the Vatican will undertake concrete steps to change the situation for the better," Alexy II was quoted as saying.

If the situation does not change it will reflect visible coolness in Orthodox and Vatican relations and "will not bring relief to people who suffer from the non-brotherly actions", the head of the Russian Orthodox Church thinks.

Gaidar - who served briefly as prime minister in the 1990s under President Boris Yeltsin and is a leader of a Russian liberal opposition party - began vomiting and fainted during a conference in Ireland on Nov. 24, and was rushed into intensive care at a hospital.

He fell ill a day after ex-KGB officer and Kremlin critic Alexander Litvinenko died in London after being poisoned with the radioactive element polonium-210.

Gaidar's aides initially said doctors treating him in Moscow suspected he had been poisoned and were working to determine how that might have happened. Irish doctors concluded he was not poisoned by a radioactive substance, but said his health had suffered sudden "radical changes."

The illness added to growing speculation in Moscow over Litvinenko's death and who might be responsible. Some critics have tied Litvinenko's death and Gaidar's poisoning to the October killing of Russian investigative journalist Anna Politkovskaya, also a Kremlin critic.

A top official with Gaidar's party, the Union of Right Forces, told Interfax on Monday that he believed Gaidar had been poisoned.

"They really tried to poison him, possibly in an attempt to discredit the authorities. There might have been other goals, but I am not ready yet to give preference to any," Nikita Belykh was quoted as saying.

"I'd rather not do any guesswork, but as far as I know, they really tried to poison him, especially if we view the situation in the light of the Politkovskaya and Litvinenko incidents," he said.

Gaidar, a liberal economist whose criticism of the Kremlin was largely limited to economic issues, served in post-Soviet Russia's most liberal and democratically oriented government. He is unpopular among many Russians who blame the liberal, Western-backed economic policies he pursued as prime minister for the decline in their living standards following the Soviet collapse.

Lawyers for Mikhail Trepashkin, a former KGB agent serving four years in jail for divulging state secrets, have said he has information relevant to the Litvinenko investigation that he wants to pass on to the detectives, Reuters news agency reports.

"Russia's prison service will not allow somebody sentenced for disclosing state secrets to continue to be a source of information for representatives of the special services of foreign states," Alexander Sidorov, a spokesman for the service, was quoted as saying.

A group of British detectives arrived in Moscow on Monday as part of their investigation into the death of Litvinenko on November 23 from a lethal dose of radioactive polonium 210.

Russia's prosecutor-general's office said on Monday it would provide them with all necessary support to carry out their inquiries.

Trepashkin, held in a Urals prison, said in a letter last Friday that the FSB, the Russian state security service, had created a hit squad to kill Litvinenko and other enemies of the Kremlin.

Litvinenko, also a former KGB agent, was one of President Vladimir Putin's sharpest critics among London's Russian emigre community. Before he died he accused Putin of having ordered his death.

The plaintiffs are members of Chabad-Lubavitch, a Hasidic Jewish movement that follows the teachings of generations of Eastern European rabbis and emphasizes the study of the Torah. The group is suing Russia to recover thousands of manuscripts, prayers, lectures and philosophical discourses by leading rabbis.

Those documents, described in court testimony as "the crown jewels" of the movement, were taken to Latvia and later Poland after Rabbi Joseph Isaac Schneersohn fled Russia in 1927. When the Nazis invaded Poland, Schneersohn fled to the United States, leaving behind the archives and manuscripts, which were seized and taken to Germany.

The Soviet Army recovered the documents in 1945 and returned them to Russia, where they are being held in the Russia State Military Archives.

Both the Nazi seizure and the Russian government's appropriation of the archives violated international law, Lamberth wrote, so the case can continue in a U.S. court.

"It's a complete victory for us. We're absolutely delighted," said attorney Marshall B. Grossman, who represents the Jewish group.

Lamberth said he had no jurisdiction to settle a dispute over a library of texts left behind when Rabbi Shalom Dov Baer fled Russia in 1915. Because it involved a Russian dispute and not a violation of international law, it could not be settled in the United States, Lamberth said.

"Clearly the library is very important to Russians," said attorney James Henry Broderick Jr., who represents the Russian government in the case. "They've set up a facility for it and they're trying to afford it the dignity it deserves."

Broderick said he was reviewing Lamberth's opinion and did not know how the Russian government would react to the archives ruling. Grossman said he would push for an early trial.

Alexey Timofeev, a spokesman for the Russian Embassy in Washington, said the government was pleased with the decision but would continue to study the ruling before discussing the judge's decision regarding the archives.