MOSCOW, Oct 30: Russia broke four days of silence on Wednesday and revealed that the gas used to subdue guerillas and end the Moscow hostage crisis was fentanyl, a potent agent responsible for nearly all of the 119 deaths among the captives.

Moscow also demanded the extradition of a top aide to the Chechen leadership after he was arrested in Denmark on suspicion of being behind the siege.

Health Minister Yury Shevchenko denied that the gas used in Saturday’s special forces operation to free the hostage was banned under chemical weapons conventions and said that the active substance in the gas was fentanyl, a powerful narcotic used as an anaesthetic.

“A fentanyl derivative was used to neutralise the terrorists,” the minister said, referring to the Chechen rebels who had threatened to execute the hostages unless Russian agreed to end the war in their homeland.

“I officially declare that chemical substances of the kind banned under international conventions on chemical weapons were not used,” he said, as quoted by the Interfax news agency.

Russian officials had previously refused to specify the nature of the gas whose effects killed most of the 119 hostages who died and has left hundreds of others still in hospital, saying only that it was an anaesthetic-type gas of a kind used in surgery.

US Ambassador Alexander Vershbow said on Tuesday that lives could have been saved if precise information had been given out immediately following the operation.

Shevchenko stressed that the substance, widely used in medical practice, “cannot in itself be called lethal,” attributing the deaths of the hostages to their poor condition after three days of captivity, notably a lack of movement and oxygen.

“These were the factors that led to the lethal outcome for some of the hostages,” he said.

Opiates such as fentanyl affect pain receptors, induce drowsiness and in sufficiently strong doses can cause the respiratory system to seize.

Shevchenko rejected widespread criticism that the doctors and hospital staff called to treat the hostages had been inadquately prepared for their task.

“The specialists were warned, myself included, although the operation had a security nature,” he said.

Medics had prepared beforehand more than 1,000 doses of antidote to the incapacitating gas pumped into the theatre to overcome the Chechen rebels, the minister added.

Medics who entered the theatre behind the special forces to help the hostages complained after the operation that they had been given little or no information or preparation and wholly inadequate material, including a lack of stretchers.

Russia had come under international pressure to divulge the nature of the gas amid lingering suspicions that banned chemicals might have been used.—AFP