Pakistan's military spokesman said on Friday the death toll in a train hijacking in the country's southwestern mountains had risen to 31 and he repeated accusations that neighbouring India and Afghanistan backed the militants who carried it out.

Terrorists in explosive vests have reportedly threatened Pakistan train passengers' lives if officials refuse to release imprisoned militants.

Pakistani officials say insurgents who attacked a passenger train carrying 440 people in the southwest killed 21 hostages but security forces rescued the others.