A memorial service to commemorate the 15th anniversary of the Beslan school siege in which more than 330 people died, the majority of them children, will be held in Moscow on Tuesday.
On September 1, 2004, 30 heavily armed Chechen separatists stormed School Number One in the Russian town of Beslan, in North Ossetia.
More than 1,100 people, including children and parents attending a back-to-school ceremony, were taken hostage.
A chaotic rescue operation by Russian special forces on September 3 led to the death of 334 people, of whom 186 were children. A further 780 people were injured.
Victims and relatives of victims blamed the authorities for the siege's deadly outcome, arguing the attack could have been prevented and that law enforcement used excessive force.
A federal investigation by prosecutors ruled in December 2005 that the authorities had not made any mistake.
But the European Court of Justice ruled in victims' favour in 2017, ordering the Russian state to pay the applicants €2,995,000 in damages as well as €88,000 in legal costs.
Judges said authorities had been "in possession of sufficiently specific information of a planned terrorist attack in the area, linked to an education institution" but that "insufficient steps had been taken" to prevent the terrorists from meeting and travelling or to increase security at the school.
They also ruled that the security operation violated Article 2 (right to life) because of "serious shortcomings in the planning and control of the security operation" and said that the use of lethal force by security forces — including tank cannon, grenade launchers and flame-throwers — "contributed to the casualties among the hostages."
Russia tried to appeal the ruling but was rejected.