Moscow: Faced with strong international and domestic pressure, Russia on October 30 disclosed that its security forces used 'Fentanyl' gas, a fast-acting opiate that has many medical applications, to end the hostage crisis in a theatre in Moscow resulting in the death of 119 captives held by Chechen rebels.

Russian Health Minister Yuri Shevchenko said that the compound was an anaesthetic and could not cause death.

Shevchenko said the security forces had not used any chemical substances banned under international treaties.

Russian medical experts attribute the high death rate among the ex-hostages to 57 hours of fatigue, stress and hunger.

The Russian Health Minister also denied media reports that medical service was not informed about the use of gas in advance.

"For the neutralisation of the gas thousand antidotes were prepared and used," he said.

Russia had previously refused to specify the nature of the gas.

Earlier, the US Ambassador to Moscow Alexander Vershbow, said the lack of information by Russian authorities "contributed to the confusion after the immediate operation to rescue the hostages was over".

"It's clear that perhaps with a little more information at least a few more of the hostages may have survived," he said.

PTI