The Russian authorities have begun negotiations with Chechen rebels who have seized a Moscow theatre and are holding hundreds of people hostage.

We condemn any terrorist attacks against civilians

Aslanbek Khadiev official Chechen rebel spokesman

Heavily-armed Russian elite troops are surrounding the building, but the security forces have said they will not attempt to intervene for now.

An MP at the scene, Gennady Gudkov, warned that the attackers were putting forward an "unacceptable demand to end to military action in Chechnya".

The attackers' leader, Movsar Barayev, says they are a Chechen "suicide" unit demanding the withdrawal of troops sent into Chechnya by President Putin in 1999 to restore Russian control.

Chechnya

Mainly Muslim region in south Russia which declared independence in 1991 Tens of thousands killed in two subsequent wars A mass Chechen hostage-taking in 1995 left more than 100 civilians dead Click here for Q&A on the Chechen conflict

But a spokesman for the official Chechen rebel leadership told the BBC he had no information about who the attackers were and condemned attacks on civilians.

"We condemn any terrorist attacks against civilians," said Aslanbek Khadiev, a representative of Chechen rebel leader Aslan Maskhadov at the Hague.

"We don't have any information about that group, and if this is a group, or just individuals - I believe some disparate Chechens are trying to bring attention to the situation in Chechnya, if they are Chechens."

Reports are coming in that two leading Russian politicians of Chechen extraction, Aslanbek Aslakhanov, and Ruslan Khasbulatov, have gone to the theatre to aid negotiations.

Threat to kill

The rebels have so far freed at least 100 people, including many women and children.

One woman among the hostages inside the theatre told Russian TV via a mobile phone that the attackers were ready to kill 10 hostages for any of their number killed if the security forces intervened.

"The only condition they are setting is that for every one of them who is killed they will immediately shoot 10 of us. So please, do not storm the building," said Tatyana Solnyshkina.

She added that the attackers had a "very large amount of explosives"

The group stormed in just as the second half of the performance was beginning in the hall - a former cultural centre at a factory on Melnikov Street in the south of the city.

Witnesses said they were wearing explosives and planting more around the theatre.

The man claiming to be the leader of the group - a nephew of Chechen warlord Arbi Barayev - said he and his followers were "suicide attackers" who had come to Moscow "not to survive, but to die".

Movsar Barayev told the Chechen rebel news agency Kavkaz-Tsentr that he and his "mujahideen" followers all had mines strapped to their bodies. He said they were accompanied by 40 widows of Chechen fighters.

'Blood in the aisles'

The theatre was holding a performance of a Russian musical, North-East, when the attack happened.

The attackers reportedly released children and Muslims immediately

"People in camouflage uniform ran onto the stage when the show was already in progress. They started shooting into the air from assault rifles," a woman who managed to escape from the theatre told Russian media.

The witness, who managed to escape as she was behind the curtain at the time, said another woman released by the gunmen saw blood in the aisles:

"They did not shoot anyone but they must have beaten people up."

Other reports say, however, that the blood may have come from an injured attacker.

The attackers released some of the hostages immediately while others managed to escape in the initial confusion.

Crisis HQ

The exact number of people taken hostage is unknown, but the play is very popular and always attracts a capacity crowd. Some reports say up to 500 people may be captive.

Special forces have been deployed at the scene

The head of Russia's Federal Security Service (FSB), Nikolai Patrushev, said that FSB and Interior Ministry special forces were at the scene and an emergency headquarters had been established.

He was keeping President Putin briefed on the situation, he added.

The official leader of Chechnya's Muslims, Mufti Akhmad-Khadzhi Shamayev, condemned the attack on Russian TV:

"Terrorists have no nationality. If they are indeed Chechens and if they are Muslims, they must have at least something sacred in them... They are just giving their nation a bad name."