Among those rescued are 17 injured passengers, who have been hospitalised for treatment.

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

The rescue operation is ongoing.

There were reports of “intense firing” at the train, a Balochistan government spokesman told local newspaper Dawn on Tuesday.

A senior police official said it “remains stuck just before a tunnel surrounded by mountains”, AFP news agency reports.

A senior army official confirmed to the BBC that there were more than 100 army personnel travelling from Quetta on the train.

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

It has waged a decades-long insurgency to gain independence and has launched numerous deadly attacks, often targeting police stations, railway lines and highways.

On Tuesday, the group warned of “severe consequences” if an attempt was made to rescue those it is holding.

“I can’t find the words to describe how we managed to escape. It was terrifying,” Muhammad Bilal, one of the freed hostages, told AFP news agency.

Allahditta, another passenger, said he was allowed to go because of his heart condition. The 49-year-old recalled how people “began hiding under the seats in panic” when the attackers stormed the train.

A local railway official in Quetta earlier told the BBC that a group of 80 passengers – 11 children, 26 women and 43 men – had managed to disembark the train and walk to the nearest railway station, Panir.

The official said the group was made up of locals from the province of Balochistan.

One man, whose brother-in-law was still being held on the train, described an agonising wait. He said he had tried to drive to the area, but many of the roads were closed.

Meanwhile, anxious families of passengers were trying to get information about their loved ones from the counter at Quetta railway station.

The son of one passenger, Muhammad Ashraf, who left Quetta for Lahore on Tuesday morning, told BBC Urdu he had not been able to contact his father.

Another relative said he was “frantic with worry” about his cousin and her small child, who were travelling from Quetta to Multan to pick up a family member.

“No one is telling me what’s happening or if they’re safe,” Imran Khan told Reuters news agency.

Officials say they are yet to communicate with anyone on the train.

The area has no internet and mobile network coverage, officials told the BBC.

Balochistan is Pakistan’s largest province and the richest in terms of natural resources, but it is the least developed.

[BBC]