U.S.-led troops mounted overnight raids on suspected al-Qaeda compounds in eastern Afghanistan, killing four people and detaining several others, officials said Sunday. The U.S. military said "several Arab fighters" were among the suspects killed or detained in the operation in Nangarhar province, although a local official said only Afghans survived. Lt. Gen. David Barno, the commander of the 18,000 mainly U.S. troops in Afghanistan, said rebels including al-Qaeda fighters were still slipping in from Pakistan. "There's continued infiltration back and forth on both sides of the border," he said in an interview after inaugurating a new U.S. base supposed to foster reconstruction in the troubled border area. American and Pakistani forces on either side of the frontier "work very closely ... to reduce that infiltration and strike back at the terrorists when they do come back and forth," he said.