The explosion on Thursday ripped through a group of Salarzai tribesmen who had formed a militia to take on insurgents in the Bajur tribal region bordering Afghanistan.

The military has encouraged tribes in Bajur to form such militias while pursuing its own airstrikes and ground offensives against militants.

The US has praised the operation in Bajur, which is considered a major stronghold for Al-Qaeda and Taleban fighters.

Police official Fazl Rabi confirmed the casualties and said the blast occurred in the Batmalai area. -- AP