Some hostages have been released after armed insurgents in Pakistan's restive Balochistan region opened fire on a passenger train carrying hundreds of people on Tuesday.
The hostages who were freed from the train said they walked for hours through mountainous terrain to reach safety. They also said they were forced to leave behind relatives from whom they were separated.
What happened?
Militants waging a war of independence against the Pakistani state created explosions on the railway track in a remote area of Balochistan, forcing the train to stop and taking more than 450 people hostage in the process.
The Jafar Express was on its way from Quetta, the capital of Balochistan province, to Peshawar in the north of the country on a 30-hour journey.
Authorities have yet to specify how many passengers were taken hostage but the insurgents said they were holding 214 people, and have threatened to start executing them.
"The affected train is still on the spot and the armed men are holding passengers," senior district police officer Rana Dilawar said.
"Security forces launched a massive operation," he said. Helicopters and special forces have been deployed.
Driver killed
The train was trapped in a tunnel and the driver was killed after sustaining serious injuries, local authorities, police and railway officials said.
The Baloch Liberation Army (BLA) claimed responsibility for the attack which took place around 1:00 p.m. (0800 GMT). They said they had bombed the track and taken control of the train.
The group also said they had taken the passengers hostage. The group warned of "severe consequences" if any attempts were made to rescue them.
Pakistan's interior minister, Mohsin Naqvi, said the government forces would not retreat and it would not make concessions for "beasts who fire on innocent passengers."
The driver was reportedly injured in the attack at which point the train came to a halt in a deserted area in the region of Bolan/Kachhi. Security guards on the train fired back.
Government spokesperson Shahid Rind said reinforcements were being sent to Bolan. German news agency DPA reported that helicopters and gunships were among the reinforcements.
"It looks [like] a terrorism attack, but we still don't know the exact situation," Rind said.
The area where the train stopped is mountainous, making it easy terrain for insurgents to launch attacks.
Who are the Balochistan insurgents?
Baloch insurgents regularly target trains, necessitating the presence of armed security personnel.
In November, a suicide bombing attack at a train station in Quetta killed 26 people, including passengers, railway staff and security guards.
The BLA is seeking independence for Balochistan, one of Pakistan's most mineral-rich but low-population provinces. The group says the central government is unfairly exploiting the region's natural resources.
It has launched attacks against the government, armed forces and Chinese interests in the region for decades.
A similar insurgency has launched attacks in the Balochistan region of neighboring Iran.