KARACHI, Pakistan 

A gun battle was underway between security forces and heavily armed militants who claimed to have taken 214 passengers hostage after attacking a train in southwestern Pakistan on Tuesday.

The outlawed Balochistan Liberation Army (BLA), in a statement to local media, claimed responsibility for the brazen attack.

The militant network, in the latest statement to local media, said they hold 214 hostages, whom it is ready to swap for "missing Baloch political activists and imprisoned BLA members."

Security forces said they have got 104 hostages, including women and children, freed, while an operation for the release of the remaining passengers is continuing.

Some 16 suspected militants have so far been killed, while several others were injured in the ongoing operation, the security sources said.

Unconfirmed reports said that at least 10 passengers, including the train driver, have been killed in the ambush.

There was no official word on casualties; however, according to security sources, 17 injured have been transported to hospital.

The incident occurred in a hilly area of the remote Bolan district in the southwestern Balochistan province when a group of militants detonated bombs on the railway track and opened fire on the Jaffar Express, which was heading to northwestern Peshawar city from the provincial capital, Quetta.

Shahid Rind, a spokesman for the Balochistan government, told reporters that additional troops have been dispatched to the site, where security forces are already engaged in a gun battle with the attackers.

Muhammad Kashif, another railway official, said the train, which is being held just outside a tunnel, comprises nine coaches, with around 500 passengers on board.

An emergency has been imposed at the nearby hospitals while ambulances and security forces were on their way to the site of the incident.

The BLA and some other groups have long been involved in attacks on security forces and citizens from other provinces.

They have been fighting for the "liberation" of Balochistan, which they contend was forcibly incorporated into Pakistan following the end of British colonial rule in united India in 1947.

Condemning the attack, Interior Minister Mohsin Naqvi said: “The beasts who fire on innocent passengers do not deserve any concessions.”