Insurgents wore U.S. uniforms in attack

• A joint U.S.-British base in southern Afghanistan comes under attack
• Two U.S. Marines die and others are wounded, a U.S. defense official says
• Joint base is where Prince Harry is stationed during a 4-month deployment
• Prince"was in no way in any danger" during the attack, an ISAF spokesman says

(CNN) -- Two U.S. servicemembers were killed early Saturday during a "sustained attack" at a joint base in southern Afghanistan's Helmand province, military officials said.

The slain Americans were both Marines, a U.S. defense official said, while three or four troops were wounded.

Attackers used a combination of small firearms and rocket-propelled grenades in their attack, according to the official.

They may have breached the "outer perimeter" of the base -- which includes the American-run Camp Leatherneck and the British-run Camp Bastion -- added the official.

Maj. Martin Crighton, a spokesman for the International Security Assistance Force, said the base came under indirect fire.

He said there were no organized demonstrations outside its gates -- as have sprung up worldwide in recent days, targeting U.S. authorities following the release of a privately produced anti-Islam video -- prior to the attack.

ISAF released a statement indicating the two deaths happened early Saturday.

By approximately 2:30 a.m. Saturday (6 p.m. ET Friday), the situation was under control and security patrols were assessing damage, said the U.S. defense official.

Exactly one week ago Friday, Prince Harry -- an Apache helicopter pilot in the British military -- arrived in Afghanistan to begin his four-month deployment, Britain's Ministry of Defense said.

He was to be based at Camp Bastion, which is in what is considered the Taliban heartland, with the 100-strong 662 Squadron, 3 Regiment Army Air Corps.

Harry, the grandson of Queen Elizabeth II and third in line to the British throne, is a captain in Britain's Army Air Corps.

The prince "was in no way in any danger" during the latest attack, said Crighton, the ISAF spokesman.