Two US Marines were killed and other Americans were wounded during a Taleban attack on a base in southern Afghanistan where Britain's Prince Harry is stationed, US officials told Reuters.
A spokesman for NATO-led forces in Afghanistan said Harry was on the base at the time of the attack but was unharmed.
"Prince Harry was never in any danger," spokesman Martyn Crighton said, adding that the NATO-led International Security Assistance Force (ISAF) would investigate whether his presence on the base had motivated the attack.
The attack involved rocket-propelled grenades, mortars and small-arms fire, with insurgents breaching the perimeter of Camp Bastion in volatile Helmand province, US officials said.
Crighton declined to offer that level of detail or give the nationalities of the victims. Crighton also did not say precisely how many people were wounded in the attack.
Earlier this week, the Afghan Taleban said they were doing everything in their power to either kill or kidnap Queen Elizabeth's grandson in what they dubbed their "Harry Operations".
A US official told Reuters that an initial report estimated five Americans were wounded but added that the extent of their injuries was unclear. The official said that this was only an initial report and that the number could change.
Crighton said the attack took place between 9pm local time and midnight on Friday and that NATO-led forces were still securing the area in and around Camp Bastion.
The motivation for the attack will undoubtedly come under scrutiny.
Violence is sweeping the Muslim world over a film that insults the Prophet Mohammad, although the Pentagon earlier said protests in Afghanistan were so far peaceful.