Authorities imposed a curfew in a north-western Pakistani city before dawn on Friday after gunmen in two separate incidents killed three Shiites and one Sunni, police and residents said.
Tension has been high in Dera Ismail Khan, a city about 290 kilometers (180 miles) southwest of the capital, Islamabad, in recent months following the killings of one dozen Sunni and Shiite Muslims in sectarian attacks.
In an overnight incident, gunmen riding on a motorcycle sprayed bullets on a Shiite and a Sunni Muslim outside a shop in the city, killing them before fleeing, said Bahawal Khan, an area police chief.
He said the latest attack came hours after, when two assailants shot and killed a Shiite lawyer, Najaf Shah, 32, and his brother Ali Shah, 38, near the city, prompting authorities to impose a daytime curfew to avoid any possible violence.
Khan said troops and police were patrolling in the city, and the situation was under their control. Pakistan has a history of sectarian violence. Although most Sunni and minority Shiite Muslims live peacefully together, extremists on both sides often target each other's leaders and activists.
The Sunni-Shiite schism over the true heir to Islam's Prophet Muhammad dates back to the seventh century.