Taimergara, Pakistan - At least seven people have been killed in an explosion near a mosque used by police officers in north-western Pakistan, officials say.
Nearly 30 people were wounded in the explosion in Lower Dir district, said hospital officials.
The Pakistani army carried out a huge operation in the district earlier this year to flush out Taliban militants.
Tens of thousands of people in the area were displaced by the fighting in the district and adjoining Swat valley.
"The bomb blast took place inside a mosque near police headquarters. At least four people have been killed," local police chief Mumtaz Zarin told AFP news agency.
"We are investigating the nature of the blast - that is, whether it was a suicide attack or planted bomb," he said.
He said the "huge" explosion had struck in Taimergara town in Lower Dir.
The local district commissioner, Fazal Kareem Khatok, said the blast took place as worshippers gathered for Friday prayers.