The exchange of fire continued for hours, but details of the losses were not yet available.

North Waziristan is a hotbed of Al Qaeda and Taliban militants launching cross-border attacks on US-led international forces in Afghanistan.

The US has launched dozens of drone strikes in Pakistan's ungoverned tribal belt, including one Aug 5 in South Waziristan that reportedly killed Pakistan's Taliban chief Baitullah Mehsud.

Although the Taliban have denied the reports of Mehsud's death, US and Pakistan officials said they are almost certain that the warlord was killed.