At least 40 people have been killed and more than 70 injured in a suicide bomb attack on a mosque in north-west Pakistan. According to local officials, the attack took place during Friday prayers in the Darra Adam Khel area. They said the roof of the Sunni mosque had caved in and the death toll was likely to rise. Witnesses said the bomber was on foot and blew himself up at the main gate of the mosque after Friday prayers had ended and worshippers were coming out of the mosque. A report said the target could have been a tribal elder who had encouraged people to take a stand against the Taliban. However, it is not clear whether he was among the victims. The mosque is in the Akhurwal village, about 45 kilometres south of Peshawar.