A group of men and women armed with guns is still holding hundreds of people who were hostages inside a theater in Moscow since late Wednesday.
A group of between 40 and 50 armed men and women took people in the theater hostage as they were watching a musical.
There are believed to be hundreds of people still in the building and the gunmen have said they will shoot hostages if police storm the building.
Valery Gribakin, spokesman for the Moscow police, said about 150 people have either been released or managed to escape.
Mr. Gribakin said the gunmen are demanding an end to the war in Chechnya.
Russian troops have been fighting Chechen rebels in the breakaway Russian republic of Chechnya since 1999.
Russian media has reported the gunmen have released about 20 children, some pregnant women and some Muslim people.
Due to the hostage crisis, Russian President Vladimir Putin has cancelled a trip to Germany and Portugal that was to take place Thursday.
One woman who spoke with VOA said she was in contact with her sister by mobile telephone. Her sister was inside the theater and had been sitting a few rows from the stage when the gunmen stormed the building. The woman inside the building reported that the gunmen said they would not start shooting unless they were fired upon by police.
Another witness, Artyom is an artist who managed to escape the theater. He spoke with Russia's TVS television.
The witness said after he heard shooting, he tried to hide. While he was running he saw a woman holding a pistol. He then managed to escape out a window.
The area around the theater is filled with police officers, soldiers, ambulances and police cars. While witnesses have heard gunshots, it is not clear yet whether anyone has been hurt.
Russian authorities have been trying to negotiate an end to the stand-off but so far with no success.
Russian troops have been fighting Chechen rebels for control of Chechnya for three years. In 1999, about 300 people in Russia were killed in a series of apartment bombings that Russian authorities blamed on Chechen rebels. Moscow later used the explosions as an excuse to invade Chechnya.
Since the fall of the Soviet Union, Russian forces have fought two wars against Chechen separatists. Russian troops invaded Chechnya in 1994 but withdrew in 1996 in a harsh defeat.
There have been earlier incidents of Chechen separatists taking hostages to draw attention to their cause or for money. The most notorious incident was in 1995 when Chechen rebels took hundreds of people hostage in the southern Russian city of Budyonnovsk.
In that incident more than 100 people died in gun battles to free the hostages.