Four NATO occupation soldiers were killed Sunday in the second suspected attack by Afghan police in two days, as officials detailed unprecedented damage from a Taliban assault on the base where Britain's Prince Harry is deployed.

Afghan authorities said the shooting took place in Zabul province, part of the restive south where the more than 10-year Taliban insurgency is traditionally strongest, but the extremist militia denied responsibility.

The US-led International Security Assistance Force (ISAF) released few details, where Ghulam Jilani, the deputy police chief in Zabul, said a police post in Mizana district came under attack, but that after NATO troops arrived to help, a policeman opened fire on the Westerners.

A senior provincial official confirmed that NATO forces came under fire, and that the Westerners returned fire, killing one policeman.

Taliban spokesman Yousuf Ahmadi said those responsible were not infiltrators. "He was just an Afghan who did this out goodwill," he said.

Sunday's deaths took to 51 the number of occupation soldiers killed since the start of the year.

Two British soldiers were killed in a similar attack on Saturday in the southern province of Helmand. The British defense ministry said they were shot by a man wearing the uniform of the Afghan Local Police (ALP) at a checkpoint.

Two US Marines were killed and several others wounded in the assault late Friday, which claimed it was carried out by at least 15 attackers dressed in US Army uniforms and armed with guns, rockets and suicide vests.

NATO on Sunday confirmed the material losses as six US AV-8B Harrier fighter jets destroyed and two significantly damaged, three coalition refueling stations destroyed and six aircraft hangars damaged.

The attackers claimed the assault was to avenge the US-made offensive film against Islam that has sparked deadly riots across the Muslim world.

Prince Harry was never in danger, officials confirmed. Although the Taliban have vowed to kill the third in line to the British throne, one of its spokesmen told AFP that the assault "had nothing to do with the prince".

On Sunday, the military also announced the arrest of a purported Taliban leader, who it said was responsible for bringing down a helicopter that killed two American troops on September 5.

The incident happened in Logar province, south of Kabul, in an area largely under Taliban control and it claimed responsibility. At the time, NATO occupation authorities said the cause of the crash was under investigation.

At least 332 occupation troops have been killed in Afghanistan so far this year, according to the iCasualties website, 253 of them American.

NATO has 112,579 troops currently deployed in Afghanistan. The Pentagon said last week that there are 77,000 US troops in the country.