Teenagers in black T-shirts bearing the words "Anti-Terror" lined up Friday at the burned-out shell of School No. 1 to remember the 333 people, more than half of them classmates, who were killed in Russia's worst terrorist attack.

Sobs echoed through the ravaged husk of the red-brick gymnasium, where terrorists on Sept. 1, 2004, herded 1,128 students, teachers and parents and rigged up bombs to start the three-day ordeal in the southern Russian province of North Ossetia .

A bell tolled to mark the time the gunmen began the assault. As melancholy music played over loudspeakers, hundreds of people filed past photographs of victims put up on the gymnasium's pockmarked walls, some lighting candles or placing red carnations on the floor in memory.

CountryWatch: Russia

The seizure ended in a bloodbath after two powerful blasts rocked the school and security forces launched a chaotic rescue effort. Most victims were killed by the explosions and ensuing gunfire or burned in the blaze set off by the blasts.

"When I think about it, my heart starts beating so madly, I'm afraid it could burst," said Shalva Khanikayev, 16, who survived but lost six classmates.

On Friday, he and friends visited the cemetery where his classmates are buried and embraced their gravestones, decorated with photographs that show them smiling.

Children elsewhere in Russia carried bright bouquets to celebrations opening the school year on what is known the Day of Knowledge — a tradition rooted in the Soviet era. Almost all Russian schools start Sept. 1, but Beslan's will open for classes Tuesday, in deference to the victims.

Some in Beslan fume at authorities over what they allege is a campaign to hide the truth and deflect responsibility for the deaths. Survivors and relatives of victims warned several officials not to attend Friday's observances.

The official inquiry concluded that all but one of 32 attackers were killed, and the sole survivor —Nur-Pashi Kulayev — was sentenced to life in prison this past May. In July,Shamil Basayev , the Chechen mastermind of the Beslan raid and other brutal terrorist attacks, died in a truck explosion.

But a study conducted by a dissident member of an official parliamentary commission and published this week punched holes in the official version, alleging that authorities were responsible for many of the deaths.

Yuri Savelyev, a lawmaker who is also an explosives specialist, alleged the two blasts that triggered the inferno were caused by grenades fired from outside — most probably by security forces — and not by bombs set by militants inside the school, as prosecutors contend.

Ella Kesayeva, who heads an activist group calledVoice of Beslan , said Savelyev's findings coincide with their own. The group on Friday appealed Kulayev's conviction and sentence to Russia's Constitutional Court, saying the lower court that heard the case ignored crucial details about the seizure and its ending.

"We have arrived at the conclusion that it's the state to blame for the death of the hostages," she said.

Asked by reporters whether the full truth of what happened would ever be revealed, regional lawmaker Stanislav Kesayev said: "Not in our lifetime."

After the attack, President Vladimir Putin began pushing through sweeping political reforms that abolished the direct election of regional leaders and strengthened the hand of pro-Kremlin parties, citing the need to strengthen protections against terrorism.

Many observers say the Kremlin used terror fears as a pretext for tightening its grip on the country, and accused the government of doing little to fight poverty and corruption that fuels violence in Russia's troubled south.

At the cemetery on Beslan's outskirts, Batraz Misikov, a 14-year-old who survived when he was carried unconscious from the burning gymnasium, walked among the new gravestones, patting those of his dead classmates.

"All those who were there are different people now," he said. "We lack words and emotions, there is only emptiness inside us."