MOSCOW - Russia acknowledged yesterday that it pumped an aerosol version of the powerful painkiller Fentanyl into a Moscow theater to end a hostage crisis Saturday, breaking a four-day silence on the drug's identity that had drawn increasing criticism in the United States and Europe.
Russia's health minister, Yuri L. Shevchenko, identified the gas as the civilian death toll from the 57-hour hostage siege rose by two to 120. All but two of the victims apparently died from effects of the Fentanyl derivative.
But at an evening news conference, Shevchenko bluntly rejected statements by some, including the U.S. ambassador here, that Russian secrecy over the nature of the gas may have delayed lifesaving aid to some hostages.
"I officially declare that chemical substances of the kind banned under international conventions on chemical weapons were not used in the course of the special operations," he said. "To neutralize terrorists, a compound based on Fentanyl derivatives was used."
In broadcast remarks, he repeated Russian assertions that the gas "cannot in itself be called lethal," and that hostages who succumbed to the gas died because they had been weakened by "a complex of extremely aggressive factors" including hunger, existing illnesses and two days of captivity.
Shevchenko's bristling defense of the rescue operation mirrored a new aggressiveness in the government's attack on Chechen terror suspects and opponents.
In Copenhagen, Danish officials acting on an international warrant seized Akhmed Zakayev, a former guerrilla field commander in Russia's first Chechnya war who has long served as an envoy for the Chechen rebels' political wing.
Russian officials had requested his arrest Friday, at the peak of the hostage crisis, as Zakayev flew to Copenhagen to attend a World Chechen Congress. A Kremlin spokesman said Zakayev was accused of armed insurrection, organizing an illegal armed detachment, and attempting to murder law enforcement officers during the first war.
The spokesman, Aleksandr Machevsky, also said there was evidence that Zakayev was at least aware of the plot by Chechen terrorists to seize hundreds of hostages in a Moscow cultural complex, but he declined to provide evidence.
In the aftermath of the hostage crisis and the rescue raid that ended it, Russia's government clearly sought yesterday to wield newfound recognition of its problems in Chechnya to its full advantage, here and abroad.
Shevchenko's admission that Russia had used a powerful narcotic to sedate the hostages and their captors appeared to be an attempt to silence growing doubts about the conduct of the rescue operation and the secrecy that has enveloped it.
American ambassador Alexander Vershbow on Tuesday called the rescue an operational success, but suggested that Russian refusal to tell doctors more about the gas used in the raid had delayed medical treatment and "perhaps" led to needless death.
His remarks echoed far stronger complaints from Moscow doctors who have said that secrecy, confusion and long delays in giving victims an antidote to the narcotic have raised the death toll.
The top health official in the Moscow city government said doctors were told of the likelihood that hostages would need treatment for a drug overdose only minutes before the rescue.
Shevchenko flatly contradicted the statements of Moscow city health officials, saying that "the specialists, including myself, were informed and warned" that a gas was to be used on the hostages and their captors.
In interviews, Russian doctors have previously said they received little or no notice that the hostages had been gassed, and that supplies of the antidote were either absent or in short supply.