As many as 25 Shia Muslims have been forced out of a bus and killed in a sectarian attack in Pakistani-administered Gilgit-Baltistan, officials have told the BBC.
The killings took place in a remote and mountainous area about 160km (100 miles) north of the capital Islamabad as the bus was travelling from the city of Rawalpindi to the city of Gilgit.
Sectarian violence has killed hundreds of Pakistanis in recent years.
Most attacks are in the Northern Areas and in Balochistan province.
Police told the BBC that those killed in the latest attack were travelling on three buses for the forthcoming Muslim festival of Eid in the district of Mansehra. They were either shot or bludgeoned to death.
The victims were checked for their identification documents, police say, before they were lined up and killed.
Police have moved the bodies to a hospital in Mansehra town, the district centre. Most victims were between 25 and 30 years of age - there were no women among them.
"Ten to 12 people wearing army uniform stopped forced some people off the buses," Mansehra administration chief Khalid Omarzai told the AFP news agency.
"After checking their papers, they opened fire and at least 20 people are reported to have been killed. This is initial information and the final toll may go up. They are all Shias," he said.
Police told AFP that the gunmen were masked.
"They stopped three vehicles, searched them and picked up people in three batches of five, six and nine and shot them dead. They were all Shias," a police spokesman said.
Correspondents say that while Shia-majority Gilgit is a popular tourist destination for wealthy Pakistanis and expatriates, it has suffered from increased sectarian tensions in recent months. The area neighbours the Swat valley, a former Taliban stronghold.
Gigit city is the capital of Pakistani-administered Gilgit-Baltistan region, and is seen as a gateway to the Karakoram and Himalayan mountain ranges.
Shias and other minority communities say those behind the violence - such as the banned Sunni militant organisation Lashkar-e-Jhangvi - are rarely caught or punished.
Sunni extremists allied to or inspired by al-Qaeda and the Taliban routinely attack government and security targets in northern Pakistan, in addition to religious minorities and other Muslim sects they consider to be infidels.
In February gunmen killed at least 18 Shia bus passengers in a sectarian attack in the northern district of Kohistan.
And in September, Lashkar-e-Jhangvi gunmen stopped a bus and killed 26 Shia pilgrims travelling on a bus in Balochistan province. The attackers were reported to have checked the identity cards of all the passengers before removing the Shias and shooting them.
A predominantly Punjabi group, Lashkar-e-Jhangvi is linked with the 2002 murder of US reporter Daniel Pearl and other militant attacks, particularly in the southern city of Karachi.