ISLAMABAD, Pakistan — At least 18 people were killed on Tuesday when a bus was ambushed by gunmen in northwestern Pakistan, government officials said. At least seven people were reported to be wounded.

Jundullah, a banned Sunni militant group, claimed responsibility for the attack, local news media reported. Extremist Sunni militant groups often target religious minorities, especially Shiites, in the country.

The bus was carrying mostly Shiite passengers to the northern town of Gilgit, according to local news reports. It came under attack in the mountainous Kohistan district of Khyber-Pakhtunkhwa Province.

Police officials confirmed that the passengers were targeted because of their faith. The gunmen made the passengers disembark from the bus and shot them one by one after identifying them as Shiites, the police said.