President Vladimir Putin was informed and was following developments, Russian news agencies reported. The presidential press service released a photo of him covering his face upon receiving the news in his Kremlin office, just 4km from the theater.
Late Friday, a mediator who met with the gunmen said they promised to release the hostages if Putin declared an end to the war in Chechnya and began withdrawing troops.
The new demands were brought out of the theater just before midnight Friday by Anna Politkovskaya, a Russian journalist who is respected by Chechens for her reporting on the war and who was called in by the rebels to mediate.
Asked if the captors seemed to be preparing to start killing the hostages, Politkovskaya said they told her: "We're going to wait only a little while."
Politkovskaya listed rebel demands, and foremost among them were Putin's declaration of an end to the war and the start of a Russian withdrawal from one region anywhere in Chechnya to show good will. If the withdrawal was verified, the rebels promised to free the hostages.
She said the captors agreed to her suggestion that verification be done by Lord Judd, a member of the Council of Europe who has made many trips to investigate the human rights situation in Chechnya.
The demand was the first time that the gunmen revealed specific conditions for freeing the hostages, who included Americans, Britons, Dutch, Australians, Canadians and Germans.
The Kremlin made only one public counteroffer, when Patrushev said that the hostage-takers' lives would be guaranteed if they freed their captives.
Daria Morgunova, a spokeswoman for the musical, told reporters that an actor who was among the hostages called her to say that the captors had threatened Friday to begin killing hostages the next morning.
The gunmen released 19 hostages Friday, including eight children aged between 6 and 12. Dressed in winter coats -- and one clutching a teddy bear with aviator goggles -- the children appeared healthy as they left the building accompanied by Red Cross workers in the afternoon.
Seven adults were freed earlier in the day, and four citizens of Azerbaijan were released after dark, Russian officials said.
Politkovskaya, a reporter for the independent Russian newspaper Novaya Gazeta, arranged earlier for the hostage-takers to accept deliveries of water and warm meals for the captives.
She was one of several influential figures who entered the theater late Friday in efforts to mediate with the captors. They also included former Prime Minister Yevgeny Primakov and Ruslan Aushev, the former president of Ingushetia, a region bordering Chechnya.
The hostage-takers have derided the Kremlin for refraining from sending high-level officials to negotiate.
Deputy Interior Minister Vladimir Vasilyev was quoted by news agencies as saying unsuccessful attempts had been made to contact Aslan Maskhadov, a rebel leader who was president of Chechnya between Russian troops' withdrawal in 1996 and resumption of the war three years later."The leader of the terrorist act is Maskhadov. It was organized with his participation."
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