Al-Qaida's No. 2, Ayman al-Zawahri, announced the "blessed union" in a video posted this week on the Internet to mark the fifth anniversary of the Sept. 11 attacks in the United States.

France's leader have repeatedly warned that the decision not to join the U.S.-led war in Iraq would not shield the country from Islamic terrorism. French participation in the U.N. peacekeeping mission in Lebanon could give extremists another reason to strike.

The national police had no immediate comment on the announced alliance, but officials have long regarded the GSPC as one of the main terror threats facing France.

French experts agreed, but also noted the group has been severely weakened by internal divisions, security crackdowns and defections in Algeria, a former French territory still working to put down an Islamic insurgency that reached its most murderous heights in the 1990s.

"The GSPC is losing speed and has suffered very significant losses in recent months," said Louis Caprioli, former assistant director of France's DST counterterrorism and counterintelligence agency.

Some GSPC fighters took advantage of a recent Algerian amnesty for Islamic insurgents and others have been killed, said Caprioli, who works for Geos, a risk management firm.

Of the 800 combatants that GSPC was estimated to have had last year, probably no more than 500 remain, and the group has had no operational cells in France since the late 1990s, he said.

But Caprioli and others also said an alliance of GSPC and al-Qaida could increase the terror risk for France - not least because al-Zawahri's designation of the country as a worthy target could inspire extremists to take action.

In his video, Al-Zawahri hailed "the joining up" of the GSPC with al-Qaida as "good news."

"All the praise is due to Allah for the blessed union which we ask Allah to be as a bone in the throats of the Americans and French Crusaders and their allies, and inspire distress, concern and dejection in the hearts of the traitorous, apostate sons of France," he said.

"We ask him (Allah) to guide our brothers in the Salafist Group for Call and Combat to crush the pillars of the Crusader alliance, especially their elderly immoral leader, America."

Although GSPC leaders had previously sworn allegiance to al-Qaida, al-Zawahri's video marked the first al-Qaida recognition of a union between the two, French terror experts said.

"From now on, the links are official, legitimate, and they are taking part in the same combat," said Anne Giudicelli, a former French diplomat specializing in the Middle East who runs the Paris-based consultancy Terrorisc.

Sarkozy said it was "not by chance" that al-Qaida used the emblematic Sept. 11 date to announce the insurgency movement's alliance with al-Qaida.

"But there is nothing new," he added, noting that the GSPC had done the same three years ago.

The GSPC, in its own statement on a Web site used by militants, confirmed the alliance and urged other militant groups to also join al-Qaida.

Giudicelli said the alliance could act as a green light for al-Qaida and GSPC militants to operate together and thus raises the risk for France.

"The Americans have become harder to target domestically, so they are trying to widen the field of action and strike their allies," she said.

Friday's attacks happened 35 minutes apart, targeting a Yemeni oil refinery in the northeast province of Mareb and a Canadian-Yemeni oil storage facility at the Dubba Port in Haramut province - scene of a 2002 attack on the French tanker Limburg, an Interior Ministry statement said.

The statement said an investigation was under way to determine the identity of the "terrorist elements" behind the attacks.

Fourteen of 23 al-Qaida prisoners who escaped from jail in February remain still at large.

In the first attack, two suicide bombers drove "at great speed" toward the Dubba Port at 5:15 a.m. in an attempt to blow up storage tanks containing a "huge amount" of oil, the ministry said.

The driver of the first car was wearing a uniform similar to those worn by staff at the facility, and the second driver was dressed in a military uniform, the statement said.

It said guards at the port "managed to blow up the rigged cars before they reached their targets."

A security guard was killed while "remains of the two terrorist attackers were strewn all over the place," the statement said. Shrapnel from the exploding cars sparked a small fire in one of the storage tanks, but it was quickly put out, it added.

At 5:50 a.m., security guards at a refinery in Mareb blew up two white cars loaded with explosives. The vehicles were similar to those driven by staff at the facility.

"They were driven by other suicide bomber terrorists who tried to break into (the facility)," the statement said.

The two attackers were killed and no one else was hurt in that attack, it said.

Saleh faces four opponents in Wednesday's elections. The most serious challenger is Faisal bin Shamlan, who was chosen by five opposition parties as their candidate.

Yemen is the ancestral homeland of al-Qaida leader Osama bin Laden and was the scene of the 2000 bombing of the destroyer USS Cole that killed 17 American sailors.

He repeated criticism of the Prophet Mohammad by the 14th century Byzantine Emperor Manuel II Palaeologus, who is recorded as saying that everything Mohammad brought was evil "such as his command to spread by the sword the faith he preached."

Most of the Pope's speech was about faith and reason but his historical references suggested that he shared the emperor's view that the Islamic concept of jihad showed that Islam was irrational and incompatible with God's nature.

Muslim clerics and leaders in many countries criticized his remarks as a sign of ignorance about Islam. But many also said they continued to value dialogue and harmony between faiths.

"While we strongly condemn and reject this talk ... we call for Muslim-Christian relations based on an in-depth scientific understanding of the mutual points of view, leaving aside sensational words," said Fadlallah.

The Muslim Brotherhood, the Arab world's largest group of political Islamists, demanded an apology from the Pope and called on the governments of Islamic countries to break relations with the Vatican if he does not make one.

The Jordanian branch of the Egyptian-based movement said the Pope's remarks would only widen a rift between Muslims and the West and revealed deep hatred toward Muslims.

The rift is already deep because of the Israeli-Palestinian conflict and wars in Iraq, Afghanistan, Chechnya and Lebanon.

Sheikh Hamza Mansour, who heads the Shura Council of the Islamic Action Front, Jordan's largest opposition party, said only a personal apology could rectify the "deep insult made by the provocative comments" to over 1 billion Muslims.

USE OF VIOLENCE

Vatican spokesman Federico Lombardi defended the Pope's lecture and said he did not mean to offend Muslims.

"It was certainly not the intention of the Holy Father to undertake a comprehensive study of the jihad and of Muslim ideas on the subject, still less to offend the sensibilities of Muslim faithful," Lombardi told Vatican Radio.

The Egyptian government, which opposes political Islamism and is friendly with Western governments, said it was worried about the effect the Pope's speech might have.

"He (Foreign Minister Ahmed Aboul Gheit) said he looked forward to intensifying efforts to strengthen the dialogue between civilizations and religions and to avoid anything that is likely to exacerbate confessional and ideological differences," a foreign ministry statement said.

Syria's mufti, or senior exponent of Islamic law, said he hoped reports of the Pope's speech were wrong and Syrians wanted to cooperate to propagate divine values.

As the Pope's historical reference showed, the dispute between Muslim and Christian religious leaders over the conditions for the use of violence is an ancient one.

The Koran endorses the concept of jihad, often translated as holy war, but there is a wide range of opinion among Muslims on the conditions for declaring and waging jihad.

Some say it applies only in cases of self-defense against external attack, as in the "just war" concept endorsed by St Augustine, Thomas Aquinas and other mainstream Christians.

Aiman Mazyek, head of Germany's Muslim council, said he found it hard to believe that the Pope really saw a difference between Islam and Christianity in attitudes toward violence.

"One only need think of the Crusades or the forced conversions of Jews and Muslims in Spain," he said.

Pakistan's National Assembly, parliament's lower house, unanimously passed a resolution condemning the Pope's comments.

"This statement has hurt sentiments of the Muslims," the resolution said. "This house demands the Pope retract his remarks in the interest of harmony among different religions."

The pontiff launched a thinly veiled attack on Islam and the concept of holy war or jihad in a speech in Germany on Tuesday, quoting a 14th-century Christian emperor who said the Prophet Mohammed had brought the world "evil and inhuman" things.

"Pope Benedict XVI has a strange approach to the dialogue between religions. He is being provocative," the paper said in its daily editorial column.

"The global outcry over the calamitous cartoons (of the Prophet Mohammed) have only just died down and now the pontiff, in all his holiness, is launching an attack against Islam," it said.

There was a wave of protests throughout the Muslim world after a Danish newspaper published cartoons of the Prophet Mohammed in September 2005 that were then reproduced by a string of other publications across Europe.

The ferocity of the Taliban resurgence since their 2001 ouster has taken U.S. and NATO commanders by surprise, particularly in southern provinces where NATO forces have been clashing daily with militants since taking control of the region on Aug. 1.

"Such blatant disregard for human life and potential undertaken by insurgents who callously ask to be called mujahedeen (holy warriors) cannot be more clear," NATO spokesman Maj. Luke Knittig said.

U.S. officials announced after a Kabul car bombing Friday that killed 16 -- including two American troops -- that a suicide bombing cell was hunting foreign troops in the capital.

Meanwhile, thousands of Canadian troops reclaimed more contested territory from Taliban fighters in the southern Kandahar province insurgent hotbeds of Panjwayi and Zhari. NATO forces claim to have killed at least 517 militants in both districts since launching a large-scale campaign on Sept. 2 dubbed Operation Medusa.

Purported Taliban spokesmen dispute the death toll and claim in videotapes that they are pushing NATO forces to the limit across the vast deserts and mountain ranges of Helmand and Kandahar provinces.

Some 8,000 Canadian, British and Dutch soldiers -- almost half of the 20,000-strong NATO force -- are leading the anti-Taliban push in the south. But military chiefs say another 2,500 troops, plus greater air support, would help them crush the Taliban threat more quickly.

In Brussels, Belgium, allied military experts failed Wednesday to commit more troops, planes and helicopters to the NATO mission, despite a plea by the alliance's American commander, Gen. James L. Jones.

"No formal offers were made at the table," said NATO spokesman James Appathurai. He told a news conference some allies had given "positive indications" on the reinforcements, but suggested final decisions may have to wait until a Sept. 28-29 meeting of NATO defense ministers in Slovenia.

In Kabul, another NATO spokesman, Mark Laity, said NATO forces were only at "85 percent of the capabilities we were told we would have" to fight between 4,000 to 7,000 insurgents believed active in the country.