Militants ambushed a Pakistani military convoy, sparking a firefight that killed nine troops Sunday in North Waziristan.

Pakistani military officials say government forces killed a number of militants in the battle, although the exact number is unknown. There also are unconfirmed reports of civilian casualties in nearby Miranshah, the capital of semi-autonomous North Waziristan

Authorities say the Pakistani convoy was ambushed near a hilltop security outpost near Miranshah. It was not immediately clear who carried out the attack.

North Waziristan, located on the Afghan border, is a major hub for Taliban and al-Qaida-linked militants. An aerial strike by an unmanned U.S. warplane in the same area is said to have killed eight or more militants on Saturday.