The bomber targeted the funeral prayers of the wife of Hakeem Khan, a leader of the "peace committee" or anti-Taliban militia of Adezai, a tribal area located near Peshawar, the capital of Khyber-Pakhtunkhwa province.
The bomber, a youth who was on foot, mingled with the mourners at Mattani, 35 km south of Peshawar, and detonated his explosive vest, district administration official Siraj Ahmed Khan told the media. Over 200 men were attending at the funeral.
At least 12 people were killed instantly while dozens more were injured, police said. Twenty injured people were taken to the Lady Reading Hospital in Peshawar. The banned Tehrik-e-Taliban Pakistan claimed responsibility for the attack, Geo News channel reported.
The anti-Taliban militia of Adezai has been at the forefront of efforts by tribesmen to flush out militants from the region around Peshawar. A former leader of the militia was killed in a suicide attack.
In recent months, leaders of the militia have complained that the government has not been providing adequate support for their efforts to take on the Taliban.
The Taliban have repeatedly threatened members of pro-government militias in northwest Pakistan. The militants want to have control on areas surrounding Peshawar so that they can gain unfettered access to the city.