BESLAN, Russia (AP) - Russian students still reeling from a hostage-taking raid in this southern town two years ago released 333 white balloons into the sky on Sunday, one for each of the victims killed in the country's worst terror attack.

In Moscow, meanwhile, riot police scuffled with a small group of demonstrators who were marking the day with a gathering near the headquarters of the Federal Security Service. About a dozen people were detained and dragged into buses.

In Beslan, students in white shirts released the balloons at about 1 p.m. — the time a series of still unexplained explosions launched the chaotic and deadly end of the ordeal that began more than two days earlier when Islamic militants seized the town's School No. 1, taking more than 1,100 students, staff and parents hostage.

A bell tolled, followed by 10 minutes of silence, and relatives and friends of victims made their way to Beslan's widely expanded cemetery to visit the graves of their loved ones.

For the third straight day, mourners filed through the blast-scarred, roofless school gymnasium that stands as a monument to the victims who were held there.

They lit candles and left flowers or bottles of water — a gesture meant to symbolically quench the thirst of victims who were denied water during the ordeal in the sweltering hall.

The third day of remembrance ceremonies in Beslan coincided with the official Day of Solidarity in the Struggle against Terrorism, which was designated by President Vladimir Putin and lawmakers last year.

It was meant as a day of remembrance of the victims of the numerous attacks that have struck Russia over more than a decade of nearly constant conflict in the Chechnya region — most of them linked to or blamed on Chechen rebels and their allies.

Events were organized to mark the day in cities nationwide, and Putin recalled the Beslan raid — which came days after bombings on two airplanes and a Moscow street killed 100 people — during a meeting with Russian Orthodox Patriarch Alexy II.

"Our meeting is taking place of the second anniversary of the monstrous crime of terrorists in Beslan," Putin said in televised comments. "The murder of innocent women and children shook not only our country but the whole world, and this tragedy, the inconsolable grief of the parents who have lost the dearest thing — their children — will forever remain our common pain."

Many relatives of victims and Kremlin critics believe the government bears much responsibility for the deaths during the Beslan hostage crisis, which ended when 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 that followed.

A Russian lawmaker and explosives specialist claimed last week the blasts were caused by grenades fired from outside the school — probably by security forces — and not by bombs set by militants, as prosecutors contend.

In Moscow, police scuffled with human rights activists, opposition politicians and other demonstrators who gathered near the headquarters of the Federal Security Service, or FSB, in hopes of placing flowers in memory of Beslan victims at a monument, some with posters blaming the authorities for deaths there.

Authorities said the group had no permission for the gathering, and at one point police began seizing people who had been told to leave.

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