Relatives of the victims of the Beslan school hostage massacre today accused Russian authorities of covering up the facts as the judge read the verdict against the sole alleged surviving attacker for a third day, describing horrific conditions inside the school.

The victims' family members said they believed Nur-Pashi Kulayev was guilty but they expressed frustration that the year-long trial had failed to reveal all those responsible for the 331 deaths - more than half of them children - in the small southern Russian town.

Judge Tamerlan Aguzarov, who has already indicated Kulayev's guilt as he sums up the case against him, read victims' accounts of the hostage-takers growing increasingly nervous and aggressive as the three-day crisis in September 2004 wore on.

By the second day, they were refusing to let the more than 1,200 captives leave the stiflingly hot sports hall where they were held to go to the bathroom.

They denied the hostages water, and many resorted to drinking urine to try to slake their thirst.

Most victims died on the third day in a hail of gunfire and explosions that erupted after one of the bombs the attackers rigged at the school went off, and security forces rushed to free hostages.

"I still have not learned the truth from the trial. I wanted to know who caused the first explosions and why my husband was killed. There is no such information and I think the authorities are purposely covering it up," said Olga Kravchenko, 74, whose husband had worked as a janitor at the school.

"This is a virtual show and it is obvious that the authorities are trying to cover things up in the Kulayev trial," said Emma Betrozova, 43, who lost her husband and two sons in the siege.

Aguzarov read a statement to prosecutors from a former hostage he identified only by her last name, Atayeva, who said that Kulayev had beaten her with the butt of an automatic rifle and had refused to allow her son to drink, the only testimony so far of Kulayev's direct role in abusing the hostages.

"There is no doubt of Kulayev's guilt, because he was among the rebels, but there is no witness testimony that he shot anyone," said Murat Kaboyev, member of a public commission established to investigate the tragedy.

"But of course Kulayev is guilty," Kaboyev said, adding that the defendant had been seen among the attackers in a room where about 20 men were shot dead early in the crisis.

Prosecutors have called for the death penalty for Kulayev, who has admitted to participating in the September 2004 attack along with some 30 other heavily-armed militants but denied killing anybody.

It was unclear, however, whether Kulayev could be executed, since Russia imposed a moratorium on the death penalty when it joined the Council of Europe eight years ago. Kaboyev said the court would need a stronger case against Kulayev to sentence him to death.

Ella Kesayeva, the leader of the Voice of Beslan activist group, said she was worried that once Kulayev's trial was over, authorities would drag out a broader probe supposed to establish all the circumstances surrounding the tragedy, not just Kulayev's role.

That investigation has been extended until July 1.

"There was premeditated murder of people by the Russian special services in Beslan," she alleged. "This is not (just) negligence.

"When people ran to the cafeteria after the initial explosions, militants put them in the windows as shields and Russian troops killed them. But nothing has been said about this in the trial," Kesayeva said.

She also said that her group had asked prosecutors to provide a photograph of a militant who was alleged to have helped carry out the car bombing that killed a senior police official and six other people in the neighbouring region of Ingushetia.

Ingush police spokesman Nadir Yevloyev said investigators suspected a militant named Ali Taziyev was one of two attackers involved in Wednesday's attack.

He refused to confirm or deny allegations that Taziyev, reportedly a former Ingush policeman turned rebel, had been among the Beslan attackers.

The conflicting reports on Taziyev underlined lingering suspicions that some of the Beslan attackers may have escaped police cordons in spite of the authorities' declaration that all except for Kulayev were killed.

Kaboyev said many different numbers of hostage-takers had come up in witness testimony during the trial.

"To this day we do not know," he said.