In an apparent suicide attack, 17 passengers of a Russian Air Force bus were on Thursday killed and 12 wounded in a powerful blast on the outskirts of Mozdok in southern Russia.

According to radio Mayak, a female suicide bomber in a white coat -- the uniform for medical personnel -- approached the bus when it slowed down at a railway crossing and triggered an explosion.

The defence ministry is rushing an investigation team to Mozdok.

All the passengers of the ill-fated bus were military and civilian employees of the local air force station, a spokesman of the North Osetian administration told PTI on phone.

"Bordering on Chechnya, Mozdok houses Russia's main air base in the Caucasus, which was widely used for attacks on Chechen terrorist bases in remote mountains," the official speaking said speaking on the conditions of anonymity.

North Osetia is the only Christian republic in Russia's Muslim-dominated Caucasus and has always been loyal to Moscow.