The terrorist attack occurred at 07:36 a.m. (0336 GMT) on Thursday when the bus was heading from a hotel in Mozdok, in the North Ossetia region bordering Russia's republic of Chechnya, to a large military base only six kilometers away.

"When the bus slowed down at a railway pass, the terrorist approached it and blew herself up," Russian Air Force spokesman Alexander Drobyshevsky said.

Of the 27 people on board, 15 were killed, including four officers, one warrant officer, three contract servicemen and seven civilians, Emergency Situations Ministry official Oleg Grekov said.

Six people were killed instantly and nine others died en route to the hospital, he added.

Colonel Nikolai Deryabin, chief of the Russian Defense Ministry's press service, has confirmed the casualties.

Officials from North Ossetia's law enforcement agencies have left for the scene, said the North Ossetian Interior Ministry.

Mozdok is a main headquarters for Russian forces fighting rebels in Chechnya.

Last month, two suicide bombings took place in Chechnya, killing at least 78 people.

(Xinhua News Agency June 5, 2003)