However, there has been no claim of responsibility for the attack, and one official suggested it could be a revenge attack by extremist Shia Muslims in the area.

"We don't know whether the Taliban, terrorists or Shiites were responsible," Abab Ali, an administration official in the main Kurram control room, told AFP news agency.

In the south of the country on Saturday, a bomb blast in Karachi - Pakistan's largest city - wounded at least 19 people.

Police said it was an apparent attack on Shia Muslims ahead of Ashoura, an important date in the Islamic calendar.

Ashoura has, in the past, been a flashpoint between Shias and the country's majority Sunni population.

Extra security is being deployed before Monday, when thousands of people are expected to pour onto streets across the country to mark the event.

During Ashoura, Shias commemorate the death of Prophet Muhammad's grandson, Imam Hussein bin Ali, 1300 years ago.