The military spokesperson said 33 militants were killed during the operation.

Twenty-one civilian hostages and four military personnel were killed by the Baloch Liberation Army (BLA) before the operation began, the military spokesperson said.

The military continues its search operation in the area to rule out any remaining threats.

The Pakistani authorities – as well as several Western countries, including the UK and US – have designated the BLA as a terrorist organisation.

The BLA is one of the rebel groups demanding either greater autonomy or independence for Balochistan, Pakistan’s largest province.

They accuse Islamabad of exploiting the province’s rich mineral resources while also neglecting it. In the past, they have attacked military camps, railway stations and trains – but this is the first time they have hijacked a train.

At least 100 of those on the train were members of the security forces, officials have said.

The militants had threatened to kill hostages if authorities did not release Baloch political prisoners within 48 hours, according to local reports.

During the attack, the militants blew up a section of the tracks and opened fire on the train near a mountain tunnel.

Officials had difficulty communicating with passengers at the time of the attack, because the remote area has no internet or mobile coverage.

Helicopters and hundreds of troops were deployed to rescue the hostages. More than 100 passengers had been freed by Wednesday morning.