A powerful bomb planted by a small separatist group derailed a train in southwest Pakistan on Thursday, wounding at least eight people, a railway official said.

The official, Suhail Ahmed, said the attack took place as the train was en route from the garrison city of Rawalpindi to Quetta, the capital of impoverished Baluchistan province. He said the explosion heavily damaged the train tracks, derailing several cars near the town of Dasht, 30 miles east of Quetta.

Shortly after the attack, the separatist United Baluch Liberation Army claimed responsibility -- saying it was in retaliation for the recent abduction of their activists by government security forces. The group warned of more such attacks in the future.

Pakistan's Railways Minister Saad Rafiq condemned the attack, calling it a "cowardly act."

He told state television that the authorities transported passengers to Quetta through buses instead.

Baluchistan has long been the center of a low-level insurgency by nationalist groups that demand more autonomy and a greater share in the region's natural resources.