Militants have taken 35 passengers hostage after attacking a train in southwestern Pakistan, and nearly 350 other passengers are believed to be safe, local police said on Tuesday.

The Baloch Liberation Army, a separatist militant group, said they had 182 hostages in total and threatened to kill them if security forces did not leave the area.

The train was trapped in a tunnel and the driver was badly wounded, local authorities, police and railway officials said.

“Around 350 passengers, including women and children are save and a relief train will be reaching the area where the train was attacked,” said a district senior police officer, Rana Dilawar.

“Security forces launched a massive operation,” he said, adding that helicopters and special forces had been deployed.

Security forces said an explosion had been heard near the tunnel and that they were exchanging fire with the militants in a mountainous area.

The BLA, which seeks independence for Balochistan province bordering both Afghanistan and Iran, said it had killed 20 soldiers and shot down a drone. There was no confirmation of that from Pakistani authorities.

The group said the hostages included Pakistan army members and other security officials travelling on leave.

Execution Threatened

“Civilian passengers, particularly women, children, the elderly, and Baloch citizens, have been released safely and given a secure route,” it said in a statement emailed to journalists and posted on Telegram.

“The BLA further warns that if military intervention continues, all hostages will be executed.”

The Jaffar Express had been on its way from Balochistan's capital Quetta to the city of Peshawar in Khyber Pakhtunkhwa province when it was fired on.

Pakistan’s interior minister, Mohsin Naqvi, condemned the attack and said the government would not make any concessions to “beasts who fire on innocent passengers”.

The Balochistan government has imposed emergency measures to deal with the situation, spokesperson Shahid Rind said, without giving more details.

The BLA is the biggest of several ethnic groups battling the government for decades, saying it unfairly exploits Balochistan’s rich gas and mineral resources.

The conflict has seen frequent attacks against the government, army and Chinese interests in the region.