The security forces have now launched a clearance operation, they said. Among those rescued are 53 men, 26 women and 11 children. Security sources added forces are continuing the operation to rescue the other hostages, and the circle around the terrorists is being tightened.

The security sources said that the injured passengers were shifted to a nearby hospital for immediate medical treatment.

Soon after the attack started, security forces cordoned off and surrounded the train, and a heavy exchange of fire was reported.

Security sources said that the terrorists behind the attack are in contact with their mastermind in Afghanistan and are using women and children as human shields.

The operation is being carried out with extreme caution due to the presence of civilians onboard.

Security sources elaborated that the operation is further complicated by the difficult terrain of the area.

The attackers bombed the railway track before storming aboard the train, said security forces, adding that they also opened fire on the locomotive, injuring the driver.

"Over 450 passengers onboard are being held hostage by gunmen," Muhammad Kashif, a senior railway government official in Quetta, the capital of the province, told AFP.

"Passengers include women and children," he added.

Security sources added that despite the challenging route, forces reached the scene in the Mushqaf area of the Bolan district of Balochistan to initiate the operation.

Spokesperson Shahid Rind said the Balochistan government has imposed emergency measures, and all institutions have been mobilised to deal with the situation.

A relief train and contingents of security forces were also dispatched to the site.

Interior Minister Mohsin Naqvi condemned the attack and prayed for the early recovery of the injured people. He added: "Beasts who opened fire on innocent passengers deserve no leniency."

Pakistan Peoples Party (PPP) Chairman Bilawal Bhutto Zardari said, "Terrorists are the biggest threat to Pakistan."  

"Targeting innocent citizens by terrorists is a coward act," he added.

Also Khyber Pakhtunkhwa Chief Minister Ali Amin Gandapur also condemned the Jaffar Express incident and expressed concern for the safety of the train passengers taken hostage in Balochistan. He expressed wishes for their safe recovery.