The U.S. military said yesterday an operation involving hundreds of U.S.-led coalition troops to hunt down Taliban and Al Qaida remnants in Afghanistan resulted in the detention of 21 suspects.

U.S. military spokesman Lieutenant-Colonel Douglas Lefforge declined to discuss the identities of those arrested in Operation Dragon Fury conducted in the Shahi Kot valley in the south of Paktia province near the border with Pakistan.

Speaking to reporters at the U.S. Afghan headquarters to the north of Kabul, he said the two-day operation that ended on Tuesday involved a 500-strong force, including 150 Italians, supported by about 20 helicopters and fixed-wing aircraft.

Lefforge said Italian forces searched 300 vehicles and 800 people in an area that has been a common route for anti-coalition forces to move in and out of the region.

He said 21 people were detained and another 13 interviewed and released, but the U.S-led forces did not come into contact with opposing forces.

The operation was one of the largest by coalition forces in Afghanistan in recent months.

Lefforge said an AH-64 Apache helicopter crash-landed during it in Paktia province, but neither of its two pilots suffered injuries. He said an investigation was under way, but hostile fire was not thought to have been the cause.

In a separate incident, four Afghan soldiers were wounded in a firefight with guerrillas at Shkin in neighbouring Paktika province, which is also adjacent to Pakistan, Lefforge said.

About 11,500 U.S.-led coalition forces are based in Afghan-istan searching for remnants of the Taliban and the Al Qaida network of Osama bin Laden, which is blamed for the September 11, 2001, attacks on the United States.

Afghan officials are convinced an increase in attacks on troops and aid workers in Afghanistan this year has been masterminded in Pakistan and have urged Islamabad to do more to catch Taliban and Al Qaida members hiding on its territory.