U.S. soldiers patrolling in eastern Afghanistan killed four men who opened fire on them in the second attack on American forces in the region in two days, a military spokesman said Wednesday.

None of the 30 U.S. special operations soldiers was injured in the attack on Tuesday north of Asadabad, which started when five people in a car started shooting at the Americans, said Col. Roger King at Bagram, the U.S. military headquarters.

The soldiers returned fire, killing four and injuring one, King said. He said no civilians were injured.

The injured man was taken to a local hospital in Kunar province and was under guard, King said. He said the men were believed to be Al Qaeda members.

A large amount of cash from an unidentified country in the region was found in the car, King said.

A day earlier, U.S. troops patrolling the same area killed two men who fired on them from a hilltop.

``Part of the process of doing patrols like this is to attempt to flush out the enemy that may be operating in that area, and then eventually drive the enemy out of an area,'' King said Wednesday. ``We view two days of contact as a success.''

U.S. forces have been in Kunar province, which borders Pakistan, for more than a month. King said the recent attacks could be a combination of a change of tactics by the adversary and changes in the way the U.S. military is operating, putting more soldiers in the field and being more active in their patrols.

``We've maintained constantly that the war is not over, that the enemy adapts and that we have to adapt our tactics to try to find him and engage him,'' King said. ``That's the bottom line of what we're here for. Our No. 1 priority is to find Al Qaeda and those people who support them and kill or capture them.''

He said the military has also expanded operations in Uruzgan province, known as a haven for former Taliban leaders, partially at the request of residents there.

On Tuesday, a provincial governor told The Associated Press that U.S. forces in Uruzgan had captured a man named Noorullah, the brother-in-law of Mullah Mohammad Omar, supreme leader of the Taliban.

King confirmed that three people have recently been detained in Uruzgan. He said they have not been interviewed yet so he could not identify them.

``We have ongoing operations in Uruzgan province,'' King said. ``Some of those operations are directed at trying to take under control former Taliban leaders, leaders of Al Qaeda, people who support Al Qaeda.''

He said the military has had about 25 percent success in those goals.

He said U.S. special forces on Tuesday uncovered two weapons caches in the village of Peca Mela in Paktika province. One cache included 34 82-mm mortar rounds, 79 rocket-propelled grenade rounds, 150 RPG boosters and several boxes of machine gun ammunition. The second cache contained 34 large rockets believed to be 122 mm, possibly Soviet style BM21s, King said.

Other coalition forces also found two small caches north of Khost in eastern Afghanistan. The caches, one found under a haystack, included 26 82-mm rifle rounds, 19 hand grenades, 3,000 rounds of 7.62 mm ammunition, three rifles and an RPG launcher.