Russian authorities have asked a Swiss negotiator to hold talks with Chechen rebels, holding up to 700 hostages in a Moscow theatre.
Michel Minnig of the International Committee of the Red Cross (ICRC) secured the release of some hostages, when he was allowed into the building to deliver medicine.
ICRC spokeswoman, Annick Bouvier, told swissinfo that Minnig had been one of two representatives allowed into the building, and had brought out a British man, who needed medical treatment.
"The representatives later entered the theatre a second time and evacuated one woman and two children," she said.
She added that Minnig, as head of the ICRC in Russia, was the main representative on the ground, but insisted that he would not be involved in negotiations with the hostage takers.
However, Russian media said parliament had specifically asked for Minnig to negotiate with the hostage-takers, who are demanding that Russia withdraw its troops from the breakaway republic of Chechnya.
Russian police were quoted as saying that a woman hostage had been shot and killed - her body was removed from the building on Thursday. There are no reports of other fatalities.
Armed with explosives
The rebels, who are thought to number about 40, stormed the theatre on Wednesday evening. They are heavily armed and media reports quote hostages as saying that they have explosives strapped to their bodies and have mined the building.
Around 60 foreigners are among the hostages, including a German-Swiss citizen and nationals from Britain, Germany, the Netherlands, Austria, Australia, Azerbaijan, Bulgaria and Belarus.
Russian president, Vladimir Putin, described the hostage taking as one of the largest terror attacks in history and claimed it had been planned by "foreign terrorist centres". He said the main task was to secure the hostages' release.
Correspondents say western accusations of Russian human rights in Chechnya have died down since Putin threw his support behind Washington's "war on terrorism", but that the current crisis is likely to test his leadership to the limit.
The Moscow siege is not the first time that the ICRC's Michel Minnig has been involved in a hostage crisis. The Swiss was the head of the ICRC's delegation in Peru in 1996 when Tupac Amaru guerrillas took nearly 700 people hostage at the Japanese embassy in Lima.
Minnig was chosen at the time the official mediator between the hostage-takers and the government. The crisis was to last 126 days before Peruvian troops were sent in.
Minnig had managed to get most of the hostages freed, despite the government refusing to free 440 Tupac Amaru prisoners it held. By the time troops stormed the compound, there were only 72 hostages left inside the embassy.
The attack carried out by the army wasn't a total success though - 17 hostage were killed along with 14 victims. Fourteen of the hostage-takers were killed, along with one hostage and two soldiers.
The Red Cross negotiator had said at the time that the result of his talks had left him with mixed feelings. But he did believe his role as a neutral intermediary had been worthwhile.
After leaving Peru in 1997, Minnig also worked in Iraq before taking up his current position in Moscow in three years ago. Among the Moscow delegation's duties are visits to Chechen prisoners held in Russian jails.
Around 40 heavily-armed Chechen separatists are holding hundreds hostage inside a Moscow theatre.
They are demanding that Russia end the war in Chechnya and pull out its troops.
Russia has asked a Swiss ICRC member to negotiate with the hostage takers.
The ICRC has already secured the release of some hostages during medicine deliveries.