Pakistan said that it has lodged a protest with the United States over what it calls an incursion into its territory by U.S. troops hunting fighters linked to the al-Qaida terror network. The U.S. military has not commented.

Both military and civilian officials said that the intrusion took place late Sunday in a remote region, known as North Waziristan, bordering Afghanistan.

They say the incident involved "a few U.S. troops" who entered about 300 meters into Pakistani territory and searched shops, but turned back as soon as they were informed they were on the wrong side of the border.

This is the first time Pakistan has publicly acknowledged such an incident involving U.S. forces. Pakistan is extremely sensitive about allowing any foreign troops on its soil. It feels any foreign troop operation could trigger massive unrest among the fiercely nationalist tribal population living along the Afghan border. Religious conservatives also have warned the government against allowing foreign troops into the country.

Foreign Ministry spokesman Masood Khan gave reporters details of the incident.

?The U.S. version is that this was a misunderstanding, that their incursion was inadvertent and when they realized that they were on the Pakistani side of the Pak-Afghanistan border, they withdrew immediately,? he explained. ?We have protested with the U.S. authorities, both through the diplomatic and military channels and requested the U.S. authorities to conduct an inquiry into the matter and share the results of this inquiry with us.?

Thousands of U.S. forces are operating in neighboring Afghanistan, mainly hunting al-Qaida fighters and members of the ousted Taleban regime. Both U.S. and Afghan officials have often complained that these fighters are using Pakistan's border regions to launch attacks in Afghanistan. Pakistan said that its military is effectively flushing out any fighters in its territory.

Earlier this week, a top U.S. military commander, Lieutenant General David Barno, questioned Pakistan's anti-terrorism strategy, particularly Islamabad's offer of amnesty to foreign militants, if they surrendered their weapons and promised to live peacefully.

Mr. Khan with the Foreign Ministry dismissed the concerns, adding that Pakistan's strategy is producing results. ?The ultimate objective here is to flush out terrorists, and we are making progress in that direction,? he said.

Pakistan said that it has captured hundreds of suspected members of al-Qaida and has conducted major anti-terror operations in recent weeks near the Afghan border. A significant number of suspected foreign terrorists are believed to still be hiding in the area.