Police say gunmen have killed a Shiite Muslim shop owner and two of his customers in an apparent sectarian attack in Pakistan.

Saturday’s attack happened in Dera Ismail Khan, a town on the Indus River in Pakistan’s northwest.

Police official Abdul Ghafoor said the family of the slain shop owner had an enmity with a Sunni Muslim militant group.

Shiite Muslims are a minority in overwhelmingly Muslim Pakistan. The two communities co-exist peacefully in most areas.

However, there have been deadly bouts of sectarian violence in the northwest this year and extremists on both sides regularly target each other.

The Sunni-Shiite schism over the true heir to Islam’s Prophet Muhammad dates back to the seventh century.