Separatist militants hijacked a train carrying more than 400 people in an isolated mountainous area of southwestern Pakistan on Tuesday.
A militant group that claimed responsibility for the attack said it was holding scores of security personnel who had been on the train, and it threatened to kill them if the Pakistani government did not agree to a prisoner exchange.
The fate of the rest of the passengers was not immediately clear, though the railway authorities said that at least 80 of them, mostly women and children, had safely reached the nearest station.
The militants, Baloch ethnic fighters, forced the train to stop in the Bolan district of Balochistan Province after opening fire on it, according to railway and police officials.
The train was traveling from Quetta, the capital of Balochistan, to Peshawar, the capital of Khyber Pakhtunkhwa Province. It was scheduled to pass through several cities, including Lahore and Rawalpindi, near Islamabad. But it became stranded inside a tunnel about 100 miles from Quetta as it came under attack, with the driver sustaining serious injuries, according to the local authorities.
Shahid Rind, a spokesman for the Balochistan provincial government, said the authorities had struggled to reach the site of the ambush because of the challenging terrain.
But security officials said that an operation was underway to rescue the passengers. A large number of helicopters were seen heading toward Bolan from the military air base in Quetta.
Rashid Hussain, a trader in the city, said his family had left on the train for Rawalpindi in the morning but had become unreachable after 2 p.m. “I am deeply worried,” he said by telephone. “The government is not providing any updates. Neither roads nor trains are safe in this province.”
The seizure of the passenger train highlighted the increasing sophistication of a separatist insurgency in Pakistan’s southwest that seeks greater political control and economic development in the region.
The attack was the latest in a series of violent episodes in Balochistan, a province bordering Iran and Afghanistan that is the site of major Chinese-led projects, including a strategic port.
A group known as the Baloch Liberation Army, or B.L.A., claimed responsibility for the train hijacking.
The group gave conflicting numbers about how many hostages it was holding.
Initially, the B.L.A. claimed it had taken 182 hostages, including members of various security agencies traveling on leave. It said it had released civilian passengers, including women, children, the elderly and local Baloch residents.
In a later statement, however, the group said it was holding at least 214 security personnel. It said it would give the government 48 hours to grant the “immediate and unconditional release” of prisoners and threatened to kill its hostages if the demand was not met.
The B.L.A.’s claim that it held large numbers of hostages could not be independently verified, and the government has yet to publicly confirm reports of hostages or casualties. In the past, separatist groups have given exaggerated figures in such cases.
Last year, the B.L.A. carried out one of Pakistan’s deadliest terrorist attacks, a suicide bombing that killed at least 25 people, including security personnel, at Quetta’s busy railway station.
The group also claimed responsibility for a deadly bombing targeting a convoy carrying Chinese citizens near the international airport in Karachi, Pakistan’s largest city. The separatists accuse the Chinese of stealing the province’s resources.
In recent months, separatist groups have escalated high-profile attacks along Balochistan’s three major highways, directly challenging the state’s authority. Last week, an alliance of the groups, including the B.L.A., announced plans to intensify attacks on Pakistani security forces, infrastructure and Chinese interests in the region.
“It points to two key trends: the increasing operational capabilities and sophistication of separatist groups and the weakening control of the government in Balochistan,” said Abdul Basit, senior associate fellow at the S. Rajaratnam School of International Studies in Singapore.
At the Quetta railway station, families of passengers aboard the train anxiously gathered at the information counter on Tuesday, seeking updates.
Many people in the region had begun to prefer rail travel after frequent militant ambushes on the highways in which passengers were killed after being taken off buses. Frequent protests have also caused road blockages.
Train services had resumed only in October after a two-month suspension because of militant attacks on railway tracks.
