Two separate gun attacks on NATO-led troops in south Afghanistan have left a total of six soldiers dead, peacekeeping force officials said, according to BBC News.

An Afghan civilian employee shot dead three soldiers, whose nationalities were not given, at a base in Helmand province on Friday, August 10.

On the same day, also in Helmand, an Afghan police officer shot three US marines after inviting them to dinner.

The killing of two British soldiers in Helmand was also announced on Friday.

There is mounting concern over attacks on NATO troops by their Afghan allies.

More than 30 international coalition soldiers have been killed in 26 attacks by members of the Afghan security forces this year, a source in the International Security Assistance Force (Isaf) told AFP news agency.

In spite of the gains made by coalition forces, and their attempts to wipe out militant leaders, almost every day brings proof that Taliban militants retain the capability to kill, BBC News said.