The blast took place in the town of Khar in the Bajaur region, in tribal areas close to the Afghan border - a Taliban and al-Qaeda stronghold.

Hundreds of people displaced by fighting had been receiving food at a distribution centre.

Reports say at least another 50 people have been injured and the death toll could rise.

Saturday's bombing was the latest in a string of recent attacks in Pakistan's north-west.

No group has so far said it carried out the attack on the centre, used by the World Food Programme and other aid agencies.

Dozens of injured people are being taken to hospital by helicopter.