As many as 40 people have reportedly been killed in a suspected suicide attack at a mosque in the Khyber tribal district of north-west Pakistan.
Officials said the blast took place as hundreds of people were leaving the mosque in Jamrud, Khyber's main town, after Friday prayers.
The semi-autonomous district's top administrative official, Mutahar Zeb, told Agence France Presse that at least 100 were injured, some seriously, with fears the death toll could rise.
There are body parts, there is mutilated flesh so we can't say whether it was a planted bomb or a suicide attack.
One witness told Reuters there were still bodies trapped in the wreckage.
According to the BBC, some witnesses said the roof of the mosque caved in after a teenage boy detonated an explosives vest.
(Read more on GlobalPost in Pakistan: Flood of US weapons in Afghanistan and Pakistan fueling militant groups)
Al Jazeera reported that television footage from Peshawar hospitals showed ambulances arriving with blast victims. The network said some of the wounded had been taken to the Khyber Teaching Hospital and the Lady Reading Hospital in Peshawar.
Taliban and al-Qaeda militants are active in the Khyber region, but no group claimed immediate responsibility for the attack.