U.S.-led forces broadened a sweep of southeastern Afghanistan for terror suspects and their allies on Tuesday, a day after collecting a large cache of weapons that could have been used by rebel fighters, a U.S. Army spokesman said.

The cache, including more than 170 rocket-propelled grenades and scores of mines and mortar rounds, was the third found since Operation Valiant Strike began in the Sami Ghar mountains of southern Kandahar province last Thursday.

Helicopters on Tuesday ferried troops to an area about 18 miles from where the operation began, Col. Roger King said, without elaborating.

"There was an air assault this morning to reposition forces to the northeast," King told reporters at Bagram Air Base, headquarters for the multinational coalition fighting terror in Afghanistan.

Some 600 U.S.-led soldiers are on the ground and hundreds more are providing support in the region as part of the new offensive to hunt for suspected Al Qaeda or Taliban fighters and their allies.

Four people have been taken into U.S. custody, but there have been no clashes with rebel fighters and no soldiers have been injured, King said. There were no new forces taking part in Tuesday's expanded operation.

Separately, just after midnight Monday, a patrol of U.S. forces from the Shkin base in the eastern Paktika province came under fire by as many as five militants, King said. No soldiers were hurt in the incident, but a Humvee was damaged after tumbling into a ditch to evade the fire.