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

The separatist Baloch Liberation Army claimed responsibility for attacking the train carrying 440 passengers in a tunnel in a remote part of Balochistan. Spokesman Jeeyand Baloch had said the group was ready to free passengers if authorities agree to release jailed militants.

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.

Insurgents who attacked a passenger train carrying 440 passengers in restive southwestern Pakistan killed 21 hostages before

Pakistan’s prime minister has commended the country’s armed forces for successfully rescuing 339 passengers after a deadly train hijacking by insurgents in the southwest

The scope of the attack underscored the struggles Pakistan faces in efforts to reign in militant groups as attacks across the country surged in recent years. Accusing India and neighboring Afghanistan has been Pakistan's go-to strategy in the past.

Hostages freed after a day-long ordeal following an attack by militants on a train in Pakistan's Balochistan province described crouching on the floor for hours before their release, as the bodies of 25 people killed arrived in Quetta.