Russian authorities breached European human rights laws when they stormed a school seized by fighters in 2004, contributing to the deaths of more than 300 hostages, the continent's rights court ruled.

However, following the ruling on Thursday, the Kremlin's spokesman objected to the ruling, saying it was "impossible" for it to "agree with this phrasing".

"Such phrasing for a country that has suffered an attack is absolutely unacceptable," Kremlin spokesman Dmitry Peskov told journalists.

Armed fighters demanding withdrawal of Russian troops from Chechnya seized around 1,100 children, parents and teachers as they celebrated the first day of the school year in September 2004.

Three days later, some of the rebels detonated explosives during a bloody shootout when Russian forces moved in.

On Thursday, the France-based court said authorities did not take necessary preventive measures to save lives.

It said the security forces' use of tank cannon, grenade launchers and flame-throwers contributed to casualties among the hostages.

It noted failures to increase security before the attack despite imminent threats against schools in the area.

The Russian Justice Ministry said it would appeal the verdict and that a number of the court's conclusions were "not backed up".

It contended that the judges failed to grasp the gravity of the situation during the siege and specifics of efforts taken to free the hostages.

The court also said Russian authorities had been aware of a possible attack on public places such as schools but had not prepared sufficiently.

"While certain security measures had been taken, in general the preventive measures in the present case could be characterised as inadequate," it said.

The court ordered that Russia pay nearly $3.2m in total compensation to the 409 surviving hostages and relatives of the deceased.

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"All the necessary legal action regarding this ruling will be taken," Peskov said, adding that the court's finding showed it did not examine the tragic events "in sufficient detail".

The head of the Mothers of Beslan group, Aneta Gadieva, said the payment ordered was meager.

"Somebody will get 5,000 euros, somebody will get 20,000 euros. That's a small sum in compensation for moral damages," she was quoted as telling state news agency TASS.