Police say a bomb exploded in a vehicle carrying security forces inside an army compound in a restive region of northwestern Pakistan, killing 15.

Police official Inyat Ali Khan says the vehicle was hired by the paramilitary Frontier Corps. It was part of a convoy that was about to leave the military base in the town of Bannu in the North Waziristan tribal area.

Khan says another 20 were wounded in the Sunday blast, and the death toll could increase.

North Waziristan is considered a safe haven for al-Qaida linked militants. Pakistani troop convoys often are hit by roadside bombs, but blasts inside a compound are rare.