Nine persons, including a relative of a Pakistan Muslim League-Q leader, were killed and several others injured in an explosion near an election meeting in Pakistan's restive northwestern Swat valley on Friday.

Police said the blast occurred near the venue of an election rally in Mingora, the headquarters of Swat district.

The meeting was addressed by former provincial minister Asfandyar Amirzaib, who is contesting the upcoming polls on a PML-Q ticket.

Among the dead was the grandson of Amirzaib, who escaped unhurt.

It was not immediately known whether the blast was caused by a suicide attacker or a remote-controlled device.

The army is conducting a major operation against pro-Taliban militants in Swat, which has witnessed a string of suicide attacks in recent weeks.