The death toll from a militant hijacking of a train in Pakistan's southwestern mountains has risen to 31 soldiers, staff and civilians, the military said on Friday as it accused India and Afghanistan of backing the insurgents.

Director General Lieutenant Gen Ahmed Sharif Chaudhry said 26 hostages were killed by the terrorists before the start of the army operation.

Pakistan's army says it has freed more than 300 hostages from a passenger train seized by militants in Balochistan province on Tuesday. The military spokesperson said 33 militants were killed during the operation.