Story highlights It appears to be the first time Afghan insurgents have worn U.S. uniforms in years

Insurgents in U.S. Army uniforms attack the camp where Prince Harry is based

The well-trained, well-armed attackers kill two Marines and destroy six jets

Four NATO troops killed by Afghan police were American, an official says

Afghan insurgents who staged a daring, well-planned raid on Camp Bastion, the military base where Britain's Prince Harry is deployed, were wearing U.S. Army uniforms, NATO said a day after the attack.

It's extremely rare for Afghan insurgents to use U.S. uniforms in their attacks. The last time CNN can identify was more than two years ago, when NATO repelled attacks on two bases in Khost province in August 2010.

No coalition troops were killed in that attack, NATO's International Security Assistance Force said at the time.

At least two U.S. Marines were killed in the brazen strike late on Friday, and six jets were destroyed, ISAF said as it released more details about the raid.

Well-trained, well-rehearsed fighters carried out the sustained assault in Helmand province, ISAF said.

About 15 insurgents organized into three teams penetrated the base's perimeter fence and did considerable damage, destroying six refueling stations and damaging six aircraft hangars.

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The attackers toted automatic rifles, rocket-propelled grenade launchers and suicide vests.

They destroyed six AV-8B Harrier jets and damaged two others before the attack ended, the coalition said.

Fourteen of the fighters were killed and one was wounded and captured, ISAF said.

Eight coalition military personnel and one civilian contractor were also wounded.

It is too soon to say whether the attackers had "inside knowledge," ISAF spokesman James Graybeal said.

ISAF would not say how the attackers got the uniforms, but CNN staff who have spent time in Afghanistan say they are for sale in markets there.

There has been at least one other case of Afghan insurgents wearing U.S. uniforms, in May 2010.

And in Iraq five years ago, there was a dramatic and successful raid using the tactic.

Attackers wearing what appeared to be American uniforms were responsible for the kidnapping and killing of five U.S. soldiers in Karbala, Iraq, in 2007.

Prince Harry is an Apache helicopter pilot based at Camp Bastion, but the British Ministry of Defence categorically rejected reports in Sunday's British press that he was just a few hundred yards away from the gun battle.

Harry, a grandson of Queen Elizabeth II and third in line to the British throne, "was in no way in any danger" during the latest attack, ISAF spokesman Maj. Martin Crighton said earlier.

On Saturday, ISAF said the camp is secure and the strike would not "impact" air and ground operations.

Camp Leatherneck, the U.S. side of the base, was not affected by the attack, Maj. Adam N. Wojack, an ISAF spokesman, told CNN.

The joint base is located in a remote desert region of Helmand, the southern province in the Taliban heartland.

The Taliban said it carried out the strike, calling it a response to the anti-Islam film stoking anger among Muslims. Yet Crighton said there had no organized demonstrations outside its gates before the assault.

Afghanistan has seen only relatively small and peaceful demonstrations against the film during a week in which there were protests across predominantly Muslim-countries and other locations.

Separately, four American troops were killed by Afghan police on Sunday, an administration official said after NATO's International Security Assistance Force reported the attack.

The latest attack on coalition troops by their supposed Afghan allies brings the number of people killed in so-called "green on blue" incidents to more than 50 this year.

The killing of the four Americans on Sunday is the latest in a series of incidents in which members of Afghan security forces have been suspected of turning their weapons on coalition or Afghan soldiers , known as green-on-blue attacks.

Sunday's killings came only a day after the British Ministry of Defence announced that two troops had been killed in Helmand province's Nahr-e Saraj district.

In that attack, a man wearing an Afghan police uniform fatally shot two members of the 3rd Battalion at a checkpoint, according to Maj. Laurence Roche, a spokesman for Task Force Helmand, said in a statement released by the ministry.

The killing occurred the same day that another British soldier died in in a separate incident in Nahr-e Saraj, according to the ministry. He was killed when his vehicle struck a bomb.