Gunmen killed two people on Monday at a rally in northwest Pakistan called to protest against sectarian clashes that left the major city of Rawalpindi under curfew all weekend.
The shooting happened in the city of Kohat while activists from the Sunni Muslim organisation Ahl-e-Sunnat Wal Jamat (ASWJ) were demonstrating against Friday's violence in Rawalpindi which left nine people dead.
"The activists were rallying against the Rawalpindi violence when unidentified gunmen opened fire on the procession from near a Shiite mosque in the area, killing two people," district police chief Saleem Khan Marwat told AFP.
Another local police official, Tanweer Ahmad, confirmed the incident.
Marwat said the ASWJ activists retaliated by firing bullets in the air, which sparked tension in the area.
Police and troops later cordoned off the area and ordered markets closed. Kohat is in Khyber Pakhtunkhwa province.
Friday's violence in Rawalpindi erupted when a procession of Shiite Muslims marking the most important day of the mourning month of Muharram coincided with a sermon at a nearby Sunni mosque.
The authorities imposed a curfew on Rawalpindi, twin city of Islamabad, which was only lifted on Monday morning. A ban on gatherings of more than five people remains in force.
Troops were also deployed in Rawalpindi as well as in the southern Punjab city of Multan to keep the peace.
Pakistan is facing rising sectarian violence, with Sunni militant groups linked to Al-Qaeda and the Taliban often attacking gatherings of Shiites, who make up some 20 percent of the country's overwhelmingly Muslim population.