An attacker wearing an Afghan army uniform has reportedly opened fire on NATO troops in southern Afghanistan, killing at least one of the foreign soldiers.

A NATO statement said that coalition forces returned fire and killed the assailant on Sunday.

"An individual wearing an Afghan National Army uniform turned his weapon against coalition service members in southern Afghanistan today, killing one service member," NATO said. The individual who opened fire was killed when coalition forces returned fire."

NATO said an investigation is under way into the attack and that the nationality of the dead soldier would be announced in his home country, but provided no other details.

The shooting is the latest in a string of attacks against US and other foreign forces by their Afghan partners or assailants posing as them.

From the perspective of one neighbourhood in Herat

The death takes the number of foreign troops killed by Afghans they were working with to at least 19 this year, in at least 13 separate attacks.

Some of the assaults have been claimed by the Taliban, who say they have infiltrated Afghan army ranks, but many are attributed to tensions between the allied forces.

Earlier on Sunday, a bomb killed three NATO service members in eastern Afghanistan, NATO said in a statement.

So far this month, eight coalition members have died in Afghanistan, bringing the year's death toll to 140.