Armed men have killed at least 19 passengers after forcing them off buses travelling from the western Pakistani city of Quetta to Karachi in the Balochistan province, authorities say.
"The attackers forced the buses to stop, abducted more than two dozen passengers, and then shot at least 19 dead," said Ismail Ibrahim, a senior official in the province.
The attack occurred late on Friday in the town of Mastung, around 40km south of Quetta.
"The armed men were wearing the uniforms of the security forces," Sarfaraz Bugti, Balochistan's home minister, said.
The bodies of 19 passengers had been found so far in nearby hills, officials said.
Akbar Harifal, deputy district commissioner, said security forces had rescued five passengers after an exchange of fire.
"Police and paramilitary have cordoned off the area and an exchange of fire is still ongoing," he said.
Fighting for decades
Separatists have been fighting a low-intensity insurgency in Balochistan, of which Quetta is the capital, for decades.
They are demanding an end to what they see as the exploitation of their resources by people from other parts of Pakistan.
Fighters also regularly attack civilian and military targets, and earlier this month at least 43 commuters were killed on a bus in Karachi in a suspected sectarian attack.
All of the victims in that attack were Ismailis from Pakistan's minority Shia community, but one security official said the Mastung incident was unlikely to have been a sectarian attack.
As well as the 19 people killed, one person was injured and five more people were rescued unharmed.