Suspected insurgents ambushed an American military convoy on a road in southern Afghanistan (search), setting off an explosion that wounded three Marines, one of them seriously, the U.S. military said Monday.

The attack occurred Saturday near the village of Dailanor, in restive Kandahar (searchprovince, said Lt. Col. Tucker Mansager, a military spokesman. The wounded men were taken to a military hospital at the U.S. base in Kandahar, the main coalition headquarters in southern Afghanistan.

Lt. Gen. David Barno, the top American commander in Afghanistan, said Monday that the military has seen a recent surge in violence, but that most attacks were directed against soft targets, such as civilians or isolated Afghan security outposts.

"We are seeing the beginnings ... in the last two weeks, of some degree of spring surge by the enemy forces," Barno said. "I think they are still dangerous, they still have the ability to conduct attacks, but those attacks are growing increasingly more focused on vulnerable populations."

Barno added that he did not believe Al Qaeda (searchleaders still have the ability to direct terrorist operations around the world from Afghanistan.

"We do not see what we call centralized command and control by Al Qaeda of varying terrorist organizations," he said, though he added that a decentralized cooperation between terrorist groups, including Al Qaeda, was possible. Usama bin Laden and his top deputy are believed to be hiding in the rugged mountains between Pakistan and Afghanistan.

Mansager said U.S. forces have more than enough military muscle to deal with the threat from insurgents. As the bloodshed has increased, military spokesmen have routinely described it as an act of "desperation" by insurgents on their last legs, echoing a line they have pushed for more than two years.

The three men wounded on Saturday are part of a contingent of 2,000 Marines who arrived in Afghanistan in recent weeks, bringing the total size of the U.S.-led coalition to about 15,500 soldiers. They are the first soldiers from the force known to be wounded in action.

Mansager said the Marines are based in southern Afghanistan, but would not reveal the location. Previously, the military would not even reveal the region of Afghanistan where the new force was operating.

Some 110 U.S. soldiers have been killed — 39 of them in combat — since Operation Enduring Freedom began in Afghanistan in late 2001. Three of those soldiers have died since the start of Operation Mountain Storm in March. Seven others have been wounded in that time.

Spc. Pat Tillman, a starting safety for the Arizona Cardinals football team who joined the Army in the wake of the Sept. 11, 2001, terror attacks, was killed by hostile fire in an ambush Thursday night in eastern Afghanistan. Two other U.S. soldiers were wounded and an Afghan militiaman fighting alongside them was killed.

Several bombings have been reported in Kandahar in recent weeks, one outside a building where the governor was holding a meeting.

A two-car U.N. convoy carrying national and international staffers working on preparations for September elections was targeted in a bombing attack on a road last week just outside Kandahar, forcing the world body to temporarily suspend all operations in the region.

The United Nations and others have warned that historic presidential and parliamentary elections scheduled for September will fail unless security is improved.

A contingent of NATO leaders were visiting Afghanistan on Monday to discuss ways to expand a 6,500-strong peacekeeping force into several northern cities and towns in the run-up to the vote.