Officials say two suspected U.S. missile strikes in northwest Pakistan have killed 13 militants.

The first attack Tuesday killed six militants and wounded six others in South Waziristan.

Three intelligence officials and one government official said a second missile later Tuesday hit a house owned by a known Afghan militant in North Waziristan. Seven insurgents died in the attack.

The officials spoke on condition of anonymity citing policy.

The tribal areas are a base for militants launching attacks both in Pakistan and on American and other NATO troops in neighboring Afghanistan. Western officials say the area is a stronghold of Al Qaeda's senior leadership.