A suicide bomber has killed at least 15 people and wounded 40 in an attack on a police checkpoint in north-west Pakistan.
The attack has cast doubt on official assertions that security offensives have weakened militants.
The bomber struck near a crowded market in Bajaur, one of the unruly Pashtun tribal regions near the Afghan border where the military has mounted offensives in recent years against the Pakistani Taliban.
Another official says at least three of the dead were policemen, including a senior officer.
