A passenger vehicle struck a roadside bomb in Pakistan's northwest tribal region killing at least five people.

Officials say the blast occurred in Bajaur agency near the border with Afghanistan.

Several others were wounded in the blast. Most of the victims were members of an anti-Taliban militia active in the area.

Bajaur agency is regarded as a stronghold for Taliban and al-Qaida militants.

Pakistani forces have carried out a number of military operations against them in the region.