At least 18 militants were killed on Friday in a US drone attack and air strikes by Pakistani combat jets on terrorist bases in the volatile Waziristan tribal region, where ground troops are preparing for a major assault against the most wanted Taliban commander Baitullah Mehsud.

Thirteen militants were killed and several others injured when a US drone fired three missiles at a militant camp in Sarokai area of South Waziristan.

Another missile was fired at a madrassa in Mantoi area though no casualties were reported as the seminary was closed, TV news channels reported.

Five militants were killed in air strikes by Pakistan Air Force jets in Datakhel area of North Waziristan agency, the channels reported.

There was no official word on the developments. Pakistani ground forces are currently preparing for an offensive against the stronghold of Tehrik-e-Taliban Pakistan chief Mehsud in South Waziristan.

The government has also stepped up efforts to woo Taliban commanders opposed to Mehsud in a bid to isolate him before military operations are launched in South Waziristan.

Today's drone attack was the latest in more than 40 such strikes by the US against militant bases in the Pakistani tribal belt bordering Afghanistan since last August.

Meanwhile, a foreign militant was killed and two rebels were injured in a clash between a lashkar or tribal militia and the Taliban in Upper Dir district of North West Frontier Province last night. The lashkar also set three houses of militants on fire.

The lashkar was formed last month to avenge the killing of nearly 50 tribesmen in a suicide attack on a mosque in Upper Dir.