Rebel fighters fired more than a dozen rockets and mortars at U.S. military positions in eastern Afghanistan, prompting an air strike that left at least two attackers dead, an Army spokesman said Monday.

The mortar and rocket fire missed their marks, and no U.S. soldiers were injured, Col. Roger King told reporters at Bagram Air Base, the headquarters of the U.S.-led coalition north of Kabul.

The attacks Sunday came a day after an ambush in southern Helmand province killed two U.S. servicemen, the first American combat deaths in Afghanistan since December and a sign rebel activity is increasing after the start of the war in Iraq.

A U.S base near the town of Shkin, in the eastern Paktika province, came under fire by about a dozen 82 mm mortar rounds, King said. Soldiers spotted three vehicles leaving the area and called in air support from a Marine AV-8 Harrier jet and two Apache helicopter gunships.

The Harrier dropped a 1,000-pound, laser-guided bomb into the cluster of vehicles, King said. The Apaches did not fire any weapons.

"The initial battle damage assessment was that we killed two individuals associated with these vehicles," King said.

Separately, assailants fired two rockets at a U.S. post in the eastern town of Gardez, in neighboring Paktia province. No one was injured.

In addition, a rocket was fired at the Kabul Military Training Center late Sunday in the capital, King said. The attack came about the same time as a rocket hit the headquarters of the international peacekeeping force that patrols Kabul. No injuries were reported.

"It was a busy night," King said.

Afghan authorities say Taliban, their Al Qaeda allies and forces loyal to a renegade rebel commander are behind the attacks.

Saturday's attack in the southern province of Helmand was the first fatal encounter for U.S. forces in Afghanistan since December.

A Special Forces soldier and an airman were killed and another Special Forces trooper wounded when their four-vehicle convoy was ambushed on a reconnaissance patrol. Three Afghan soldiers also were wounded.

The Americans killed were identified by U.S. authorities and family members as Army Special Forces Sgt. Orlando Morales, 33, of Manati, Puerto Rico and Staff Sgt. Jacob L. Frazier, 24, a member of the Illinois Air National Guard from St. Charles, Ill.

The ambush took place two days after an international Red Cross worker was killed in neighboring Kandahar province. The region is the birthplace of the hardline Taliban regime driven from power by U.S.-led forces in late 2001.

U.S. forces and Afghan militia have been conducting sweeps in Kandahar province -- and such offensives often spur more rebel activity.

Hundreds of coalition forces swept into the Helmand Valley last month for Operation Viper, and patrols of the perilous area continue.

The ambush was part of an "uptick" in rebel activity following the start of the Iraq war about 10 days ago, he said.

Posters supposedly written by the Taliban's elusive leader Mullah Mohammed Omar have recently appeared in eastern Afghanistan renewing his call for a holy war against U.S. troops and Afghans who work with them.

"Whenever the non-Muslims attack a Muslim land it is the duty of everyone to raise against the aggressor," said the posters, which carried the signatures of 600 Islamic clerics.

"We were blamed for Usama bin Laden because they said he was a terrorist and he was taking shelter with us. But what is the fault of Iraq? Iraq has no Usama bin Laden in his country," it said.