HELMAND PROVINCE, AFGHANISTAN (CNN) -- Two U.S. Marines 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.
© The British Camp Leatherneck in Helmand province, shown in a 2010 file photo, is part of the joint base that was attacked Friday.
