MOSCOW -- At the Kremlin's urging, Denmark arrested a key aide to Chechen leader Aslan Maskhadov in the deadly raid on a Moscow theater and other terror attacks -- further evidence of Russia's success in isolating a rebel movement whose envoys were once received in capitals around the world, including Washington.
Russia also acknowledged for the first time Wednesday that the powerful opiate fentanyl was used in the rescue operation that killed at least 119 hostages.
Health Minister Yuri Shevchenko insisted the compound was an anesthetic that would not cause death under normal circumstances.
Most agree the decision to pump the sedating fumes into the theater early Saturday ended the crisis; it incapacitated the heavily armed Chechen hostage-takers, preventing them from setting off explosives, and led to the rescue of more than 660 theater-goers.
But, Shevchenko acknowledged, it was likely fatal for many of the hostages, who were weakened after sitting in cramped quarters for 58 hours, deprived of food, dehydrated and under severe psychological stress.
"It is precisely these factors which led to a lethal outcome for some of the hostages," Shevchenko said.
Fentanyl is most often prescribed as a painkiller, and is usually administered by injection, with a lozenge that dissolves on the tongue, or through a skin patch. Higher doses can be fatal, drug literature warns, and doses must be adjusted according to the patient's size and their previous exposure to similar drugs.
The attackers stormed the theater on Oct. 23, taking an audience of about 800 people hostage and demanding that President Vladimir Putin pull troops out of Chechnya.
Russian officials accuse Maskhadov, the elected president of Chechnya's separatist administration, of being behind the attack, though they have not offered evidence and Maskhadov has denied any connection.
Maskhadov, once seen as key to any political settlement in Chechnya, has sent envoys to world capitals, including Washington. But he has been increasingly sidelined by the Kremlin, and the arrest of his envoy in Copenhagen further boosted Moscow's efforts to isolate Chechen leadership.
Akhmed Zakayev, who has denied links to terrorism and expressed willingness to start unconditional peace talks with Russia, was detained at his hotel before dawn Wednesday after Danish authorities received documents from Russia via Interpol. He was in Denmark for a Chechen conference.
Meanwhile, Shevchenko's revelation about the drug used in the theater rescue was likely to win the Kremlin some relief from foreign governments, which had pressed for more details for days.
The U.S. Ambassador to Moscow, Alexander Vershbow, said Tuesday that "with a little more information at least a few more of the hostages may have survived."
Shevchenko defended the actions of medical workers, saying more than 1,000 doses of an antidote had been prepared to help the hostages. But some Russian doctors have said they were given very little information about the type of gas used.
Shevchenko did not name the antidote. Doctors say the effects of opiates like fentanyl can be countered by the drug naloxone.
The gas continued to claim lives, with two more hostages dying overnight, said Lyubov Zhomova, a spokeswoman for the Moscow health committee.
As of late Wednesday, 152 rescued hostages remained hospitalized, the ITAR-Tass news agency reported, citing Moscow health authorities. A total of 501 patients had been released, but many would require further treatment, Interfax news agency reported.