Updated

U.S.-led forces killed three insurgents in a gunbattle at a cave complex in southeastern Afghanistan (search), the American military said Monday.

The skirmish was the first reported by the U.S. military since the start of a new operation on March 7 designed to intensify the campaign against a stubborn Taliban (search)-led insurgency and to track down terrorist leaders including Usama bin Laden (search).

Meanwhile, two U.S. airmen were wounded, one of them seriously, by an old mine at Bagram Air Base, the main American camp north of the capital Kabul (search).

The gunbattle occurred Saturday morning as dozens of troops, including special forces, searched the cave complex southwest of Qalat, the capital of Zabul province, some 240 miles southwest of Kabul, spokesman Lt. Col. Bryan Hilferty said.

He said the coalition troops, who were armed with rifles and machine guns, also came under fire, but none were reported injured.

"We surprised them," Hilferty said. "I don't know who started the engagement."

Troops, including special forces, arrested five militiamen in the caves on Saturday and discovered "anti-coalition propaganda," Hilferty said. He had no details.

Hilferty said eight more suspects were detained in the same area Sunday.

Zabul is one of the provinces along the rugged Pakistani border where Taliban guerrillas are believed to have taken refuge after the ouster of the hardline Islamic regime by a U.S.-led coalition in late 2001.

The military announced a new operation, dubbed "Mountain Storm," on Saturday as part of a drive to crush the militants and capture their leaders, and make the region safe for reconstruction and summer elections.

As well as the Zabul raid, the military has said U.S. troops were involved in an air-assault last week, but has not given any details.

More than 160 people have died in violence this year in Afghanistan, including aid workers and government employees as well as Afghan and foreign troops.

On Saturday, suspected Taliban armed with rockets and heavy machine guns attacked a government office near the border in Kandahar province, sparking a gunbattle that left three attackers and one Afghan soldier dead and two soldiers wounded, officials said.

Some 70,000 Pakistani troops have moved into semiautonomous tribal regions to take away maneuver room for Al Qaeda and Taliban fugitives believed to have taken refuge there.

Hilferty said the two American airmen were injured when a mine exploded at Bagram on Saturday.

"We believe it was just an old one left over from the wars here," he said.

The most seriously injured of the airmen was evacuated to Germany for treatment. The other was under observation at Bagram, he said. The soldiers were not identified.