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.

The Pakistani Taliban has claimed responsibility for the attack. A Taliban spokesman said the attack was revenge for the killing of its members.

Pakistan's Taliban has mounted suicide bombings which have often killed civilians, and shooting attacks on security forces in an effort to topple the government.

Pakistan has been unable to stop the Taliban's attacks.