The strike came two days after a visit to Islamabad by Admiral Mike Mullen, the top US military official, in which he expressed concern over links between Pakistani security agents and militants attacking U.S.-led forces across the border in Afghanistan.

The drone strike happened in Mir Ali town, about 35 km (20 miles) east of the region's main town of Miranshah.

North Waziristan is a known sanctuary for al Qaeda and Taliban militants.

The United States has been using drone attacks to target militants over the past few years in Pakistan's lawless ethnic Pashtun border areas.