Gunmen riding a motorcycle opened fire with automatic weapons on a government bus carrying the worshippers to Friday prayers, Tariq Jameel, a deputy inspector general of police, told Reuters.

"Five people have been killed and seven others wounded," he said. "We have launched investigations."

Police said the gunmen had fled the scene.

No group has claimed responsibility for the attack, but police blame Sunni Muslim militants for most of the sectarian bloodletting in Pakistan.

Hundreds of people, mostly Shiite Muslims, have been killed in sectarian violence in Pakistan in recent years. At least 57 Shiite worshippers were killed in July in an attack on a mosque in the southwestern city of Quetta.

Pakistan is a predominantly Sunni Muslim nation, with Shiites accounting for about 15 percent of the country's 149 million people. The two communities largely live at peace with each other and violence is restricted to the militants.