Pakistani police say a suicide bomber crashed an explosives-laden car into a police checkpoint killing at least three officers and wounding 17 others.
Officials say Monday's early morning attack occurred in northwest Pakistan, near the North Waziristan tribal region bordering Afghanistan.
No one has claimed responsibility for the incident.
Many Taliban and al-Qaida militants fled to Pakistan from neighboring Afghanistan after the U.S.-led invasion in Afghanistan toppled the Taliban in late 2001. Insurgents have a strong presence in Pakistan's volatile tribal areas.
Some information for this report was provided by AFP, AP.