Gunman in Afghan army uniform kills two NATO troops

A man in Afghan army uniform shot dead two NATO soldiers in southern Afghanistan on Monday, raising to 13 the number of foreign troops to die in a series of such killings this year.

Almost one in seven of the 90 foreign soldiers to have died in Afghanistan this year has been killed in so-called "green-on-blue" attacks, raising tensions between NATO forces and their local colleagues.

A key strategy of NATO's US-led mission in Afghanistan is training Afghan forces to take over national security by the end of 2014, allowing foreign combat troops to withdraw after a costly and lengthy war against the Taliban.

"An individual wearing Afghan army uniform turned his weapon against International Security Assistance Force service members in southern Afghanistan today, killing two," ISAF spokesman Major Jason Waggoner told AFP.

Coalition forces returned fire and killed the gunman, he added, declining to specify the victims' nationalities.

A senior Afghan official told AFP the incident happened at a US-run base used by civilian and military personnel working in a provincial reconstruction team in Lashkar Gah, the main town in Helmand province.

The gunman approached the base from outside, he said, where there was "apparently" an argument and the man opened fire.

Lashkar Gah was among the first places in Afghanistan where responsibility for security was handed over from ISAF to Afghan forces as part of a gradual transition process.

The fatalities from previous green-on-blue attacks this year have been six Americans, four French army trainers and an Albanian.

The frequency of the incidents reached a peak after copies of the Koran were burned at an incinerator pit at the US-run Bagram airbase, leading US President Barack Obama to apologise for what he described as an error.

Around 40 people were killed in days of violent demonstrations as protesters targeted Western bases. At one point NATO withdrew all its advisors from Afghan government ministries after two American officers were shot and killed inside the interior ministry, apparently by an Afghan colleague.

On March 11, a massacre of 17 Afghan civilians, including nine children and four women, blamed on a lone American soldier brought relations between Kabul and Washington to a further low.

A classified report leaked to The New York Times earlier this year described green-on-blue shootings as a "systemic" problem.

The report put the killings down to a decade of contempt on each side, and profound ill-will among both civilians and soldiers on both sides, downplaying the role of possible Taliban infiltrators in such incidents.

An ISAF statement released in Kabul said a joint Afghan and NATO investigation had been opened into the latest killings.