Two gunmen holding 35-people hostage on a bus in southern Russia are demanding the release of five Chechens jailed on hijacking charges. Special anti-terrorist forces have deployed around the bus.
Security officials in southern Russia say negotiations with the gunmen are underway and that food and water will be provided as the standoff continues.
The bus is stopped on a highway bridge near the airport at Mineralnye Vody, 900-kilometers south of Moscow.
The two gunmen are believed to be armed with a submachine gun, a hand grenade, and one-kilogram of the explosive TNT. The gunmen are demanding freedom for five Chechens serving prison terms for a 1994 bus hijacking in the same region.
Russian Interior Minister Boris Gryzlov says the primary concern is to free the hostages, but added no one is going to make concessions to terrorists.
Television pictures showed troops and armored vehicles taking up positions in the area around the bus. Russia's elite Alpha anti-terrorist group was dispatched to the scene along with a team of hostage negotiators.
Temperatures reached 38C and a doctor was allowed on board to tend to some hostages who were complaining of chest pains.
Six passengers were released earlier, including a man who had suffered a gunshot wound.
The bus was seized near Stavropol and began making its way to airport at Mineralnye Vody. The city is a popular resort town in the Caucasus Mountains not far from Chechnya, where a separatist rebellion has been under way for nearly a decade.
That part of southern Russia has been the scene of several bus hijackings and bombings in recent years. In 1992, two armed men hijacked a bus with 18-people on board. There were two bus hijackings in 1994, including an incident in which five hostages and a kidnapper were killed and 15 people were wounded.