Officials say a suicide bomber in Pakistan's restive northwest tribal region, along the Afghan border, has killed 20 people and wounded at least 40. Five policemen are among the dead.

Authorities say the bomber detonated his explosives Friday as he approached a police checkpoint, near a market in Khar, the main town of the Bajaur tribal district.

Officials say no group has claimed responsibility for the attack, but the Pakistani Taliban has carried out similar attacks in the past.