Gunmen wearing military uniforms stopped a convoy of buses in northern Pakistan, ordered selected passengers to get off and then killed 16 of them in an apparent sectarian attack.

The victims were Shi'ite Muslims, a minority in Pakistan that is frequently targeted by extremists from the majority Sunni community. The gunmen spared several dozen other people in the four-bus convoy.

A spokesman for a faction of the Pakistani Taliban, a Sunni militant group, later said it carried out the killings.

The incident in the remote Kohistan region was the latest in recent weeks that has demonstrated the resilience of militant networks, including al Qaeda-allied groups.

The attack happened in the mountainous village of Harban Nala, just over 200 miles north of the capital Islamabad. The area, part of the famed Silk Road linking northern Pakistan to China, is populated by Sunni tribes.

Police officer Mohammad Azhar said the buses were travelling from Rawalpindi city to Gilgit when the gunmen attacked.

Eight gunmen were involved in the ambush, and all were wearing military uniforms, presumably to make it easier to stop the buses. The attackers ordered the passengers to produce their identity cards before ordering the 16 off and shooting them.

Fear of attacks on travellers had increased after an incident last month in which an unknown number of Sunnis were killed in the Gilgit region.

Buses have since been travelling in convoys as a security measure.

Sunni extremists allied to or inspired by al Qaeda and the Taliban routinely attack government and security force targets, as well as religious minorities and other Muslim sects they consider infidels.