Attackers hurled a grenade into a jeep carrying two U.S. soldiers and an Afghan interpreter in the heart of Kabul on Tuesday, wounding all three, the U.S. military said.

One of the soldiers was wounded in the head and "in the lower extremities," while the second soldier suffered wounds to the lower right leg, said Lt. Tina Kroske. She did not identify the soldiers or say how serious their injuries were.

The interpreter's condition was not immediately known.

Kroske said three suspected assailants were arrested, but Kabul Police Chief Basir Salangi said only two men were in custody.

He identified them as Amir Mohammed, of Khost in eastern Afghanistan, and Ghulam Saki of Jalalabad, the capital of Afghanistan's eastern Nangarhar province.

Mohammed was arrested with at least two grenades in his pocket, Salangi told The Associated Press.

Four U.S. Humvees equipped with machine guns guarded the site of the attack, on a crowded corner in front of city's Blue Mosque. A policeman at the scene, speaking on condition of anonymity, said he saw a boy throw a grenade toward the vehicle and witnessed a second man, gearing up to throw another grenade, tackled by a fruit vendor.

Attacks against U.S. service personnel in eastern Afghanistan, and in particular in Khost, are routine.

Tuesday's attack was the latest in a series of sporadic attacks on U.S. soldiers in Afghanistan, following a Nov. 28 incident in which a sniper shot a U.S. Special Forces soldier in the leg in eastern Afghanistan. The shooter escaped.

Fifteen U.S. servicemen have been killed in combat or hostile situations in Afghanistan since the U.S.-led anti-terror campaign began last year. The most recent fatality was on May 19.