Islamabad, December 25: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.
About 1,000 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.
Civilians
Saturday’s bombing was the latest in a string of recent attacks in Pakistan’s unruly 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 to distribute food to conflict-affected people in the region.
“I myself have counted 40 bodies but the death toll could rise as several wounded people are in critical condition,” Dosti Rehman, an official at the main government hospital in the region, told Reuters news agency.
Dozens of injured people are being taken to hospital by helicopter.
Most of the victims are believed to be civilians who had fled the fighting between Taliban militants and the Pakistani army, the BBC’s Aleem Maqbool in Islamabad reports.
The tribal district of Bajaur, where the attack took place, has seen several military operations to clear it of insurgents – the army had previously declared the operations a success, and the area safe for the displaced to return to, our correspondent adds.
Among recent other attacks, at least 11 Pakistani soldiers and 24 militants were killed on Friday after some 150 Taliban fighters attacked five Frontier Corps checkpoints in the neighbouring Mohmand tribal region.
Earlier this month, a suicide bomb attack in Mohmand left at least 40 people dead.
A double suicide bombing in Mohmand in July killed more than 100.
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—Agencies