Pakistani forces on Wednesday launched a full-scale operation to rescue train passengers taken hostage by militants in the mountainous south-western part of the country.

It was gathered that more than 450 passengers were on board when militants captured the train at the entrance of a tunnel in a remote frontier district, with an unknown number of hostages still being held.

Militants reportedly bombed a section of the railway track and stormed the train on Tuesday afternoon in southwest Balochistan province, which borders Iran and Afghanistan, where attacks by separatists have been on the rise.

According to security sources, the terrorists had positioned suicide bombers right next to innocent hostage passengers

Three people were killed, including the train driver, during the siege in mountainous Sibi district.

A senior government railway official in the provincial capital Quetta, Muhammad Kashif, on Tuesday afternoon said that the 450 passengers on board had been taken hostage.

Meanwhile, the Baloch Liberation Army, BLA, a separatist group that has staged a series of daring recent attacks against security forces and ethnic groups from outside the province, immediately claimed responsibility for the assault.

The group has demanded an exchange with security forces for its imprisoned members.

Pakistani forces launch operation to free train hostages