KABUL — Two soldiers in the NATO-led coalition fighting insurgents in Afghanistan were shot dead Tuesday by a man in an Afghan police uniform, the alliance's International Security Assistance Force said.

It is the latest in a series of insider attacks that have seriously undermined trust between NATO forces and their Afghan allies in the fight against hardline Islamist Taliban insurgents.

"An individual wearing Afghan National Police uniform turned his weapon against ISAF forces in southern Afghanistan, killing two soldiers," a spokesman told AFP.

The Taliban claimed that the shooter was one of their fighters who had infiltrated the police and that the soldiers killed were British.

"One of our mujahideen, Atiqulla, who had infiltrated the police forces carried out the attack in Greshk district (Helmand province) today," Taliban spokesman Qari Yusuf Ahmadi told AFP.

"He has killed two British soldiers."

Helmand governor Mohammad Naim Balooch confirmed the shooting had taken place in Greshk district and that two foreign soldiers were killed.

In London, the Ministry of Defence said the two soldiers killed were serving with the British army's Royal Gurkha Rifles regiment. A ministry spokeswoman would not confirm if they were British or Nepalese.

It is the second deadly incident in a week for NATO in Greshk, which is also known as Nahr-e Saraj, after a British Royal Marine and army medic were killed while on patrol last Wednesday.

The Afghan conflict has seen a surge in insider attacks this year, with more than 50 ISAF troops killed by their colleagues in the Afghan army and police.

NATO says about 25 percent of the attacks are caused by Taliban infiltrators but the rest stem from personal animosities and cultural differences between Western troops and their Afghan allies.

In the most recent previous attack, two American soldiers were killed by a man in an Afghan police uniform in the central province of Uruzgan last Thursday.

The unprecedented number of so-called "green-on-blue" killings comes at a critical moment in the 11-year war, as NATO troops prepare to withdraw by the end of 2014 and hand responsibility for security to Afghan forces.

NATO top brass have admitted the seriousness of the phenomenon, with ISAF commander General John Allen saying that just as homemade bombs were the signature weapon of the Iraq war, in Afghanistan "the signature attack that we're beginning to see is going to be the insider attack".

US Defence Secretary Leon Panetta told a meeting