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.

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.

Baloch separatist militants blew up a railway track and launched rockets at the Jaffar Express, which was carrying over 400 passengers.

Nearly 200 have been freed but the status of other passengers remains unclear as security forces continue to battle separatist militants.

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.

Indian government dismissed Pakistan's claims of its involvement in Jaffar Express attack, urging Pakistan to confront its own problems rather than shift blame.