A NATO soldier in the eastern Afghan province of Kunar has been shot dead by a man in an Afghan army uniform, officials say, according to BBC News.

NATO says the incident is under investigation.

There have been a growing number of cases where Afghan soldiers have killed NATO colleagues. At least 18 foreign troops have been killed in "rogue shootings" this year.

Observers say this has eroded morale among foreign forces. Only Taliban bombs have killed more foreign troops this year.

A NATO statement gave no further details about Friday May 11 attack and did not specify the nationality of the dead soldier.

But local officials in eastern Afghanistan confirmed the incident took place in Kunar province.

"An Afghan army soldier turned his weapon against U.S. soldiers inside an Afghan-U.S. military base in Kunar province, killing one U.S. soldier and injuring two others," provincial police chief Ewaz Mohammad Naziri told the AFP news agency.

Members of the NATO-led Isaf force are training their Afghan counterparts in preparation for a full handover of responsibility for security by 2014.

Revelations in February that U.S. troops burned copies of the Koran at a base in Afghanistan - reportedly by accident - as well as the shooting of 16 Afghans by a U.S. soldier in March have inflamed public opinion against the foreign forces.