Pakistani troops fired at two United States helicopters that intruded into the restive North Waziristan tribal region, forcing them back to Afghanistan, a media report said on Monday.

The gunship helicopters apparently intruded into Pakistani airspace at the border village of Lowara Mandi in North Waziristan Agency before they were fired at by Pakistani forces on Sunday night, The News daily reported.

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Government officials, including those from intelligence agencies, told reporters in Miranshah, the headquarters of North Waziristan, that the incident occurred at 10 pm (local time). They said the helicopters entered Pakistani airspace and flew over Lowara Mandi.

Pakistani soldiers used 12.7 mm light machine guns to fire at the helicopters, forcing them to fly back across the border to Afghanistan, the officials said.

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Reports from Lowara Mandi said local tribesmen too fired at the helicopters, which did not attack any targets in Pakistani territory.

Pakistan has protested angrily against cross-border missile strikes and an incursion by US-led coalition forces in Afghanistan, saying only its forces have the right to operate in the country's territory.

It has also vowed to retaliate against any operations within Pakistani soil by foreign forces.

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