"The situation is very tense," Georgi Vassiliyev, director of the musical that was being performed in the theatre, told his wife by mobile phone.

All hostages and terrorists are highly strung. The first attempt at an assault will lead to a powerful explosion

Georgi Vassiliyev, musical director

"All hostages are kept in the auditorium. They were not given food or water. The orchestra pit is used as a lavatory."

Danila Galperovich, of the BBC Russian Service, said news from the theatre on Friday morning was that the hostages had been separated, with about 180 of them being kept on the first floor, and the rest on the ground floor.

Our correspondent said that some hot food had now been delivered and warm clothes and medicine had also been taken in by the Red Cross.

But overnight a hot water pipe had burst and was flooding the ground floor, Federal Security Service spokesman Sergei Ignatchenko told the Associated Press news agency.

He said that the hostage-takers had called the flooding a "provocation" and no agreement had been reached on having the pipe repaired.

Explosives prepared

Mr Vassiliyev said that a powerful bomb had been laid in the centre of the theatre hall and that the stage and the aisles had been mined.

In a transcript of his conversation, broadcast by the German ARD television station, he said: "Approximately 15 armed people, men and women, stay constantly in the auditorium.

"They are wrapped in explosives. They watch all the aisles, wings and the basement for the attack team to appear.

"All hostages and terrorists are highly strung. The first attempt at an assault will lead to a powerful explosion."

The siege is taking its toll on relatives of the hostages

A doctor who was allowed in to examine the hostages with a film crew from the television station NTV, said most of the hostages were calm.

Dr Leonid Roshal, head of the Medical Centre for Catastrophes, said that only "two or three" of the hostages were hysterical.

He said he had some minor ailments including eye problems, coughing and hypertension.

"There are some people who are unwell but it is the psychological pressure that is hard," he said.

Discomfort

Dr Roshal said the rebels were not beating or threatening their captives.

Briton John Leonard, whose sister-in-law is one of the hostages, said he had spoken to her by mobile phone and she had told him the guerrillas had explosives tied to chairs, as well as fixed to the stage.

She described the situation as uncomfortable but calm.

"The demands of the terrorists are very clear and the hostages want to know what is going on outside," Mr Leonard said.

"They are well aware that the terrorists have said that they will blow up the theatre if the security forces attempt to storm it

"They have not been deliberately malicious."