The troops intruded into a border village in the North Waziristan tribal region on Thursday and searched several houses before moving back into Afghanistan, military spokesman Major-General Shaukat Sultan said.

"We have already lodged a protest with the United States," military spokesman Major-General Shaukat Sultan said.

Earlier this month, US troops intruded into the same region and searched shops and a petrol station, prompting a protest from Pakistan.

The Pentagon has said the incursion was inadvertent but Afghan officials and US have repeatedly charged that al-Qaeda and Taliban fighters have launched attacks inside Afghanistan from the safety of Pakistan's tribal region.

The latest incursion came on the day that Pakistani President Pervez Musharraf vowed to eliminate al-Qaeda militants hiding in Pakistan's wild tribal region.

Pakistan, a key ally in the US-led "war on terror", has deployed thousands of its own troops on its Afghan border to round up foreign militants but has said it would not allow US forces to operate inside its territory.