NATO says two men wearing Afghan police uniforms have turned their weapons on coalition troops in southern Helmand province Saturday, leaving two service members dead.
A NATO statement said one of the shooters was killed when coalition forces returned fire, while the second managed to escape and was being pursued. The nationalities of the victims were not released, but the French news agency cited Afghan sources as saying the service members were British soldiers based in Helmand.
The incident is under investigation and comes a day after an attacker wearing an Afghan army uniform shot and killed a U.S. service member in eastern Kunar province. Saturday's shooting brings the number of incidents - in which Afghan soldiers or insurgents disguised as soldiers fired on coalition forces - to 16 this year alone.
Separately, four more coalition troops were killed Saturday in three separate incidents in southern Afghanistan. NATO said two soldiers died in an insurgent attack, another was killed in a bomb blast and the last one died as a result of a non-battle injury. The nationalities of the victims were not released.
In northwestern Badghis province, four Afghan policemen died when their vehicle hit a roadside bomb.
U.S. officials say many of the so-called "insider attacks" are motivated by personal disputes.
The incidents have raised concerns about security in Afghanistan at a time when international combat troops are preparing to withdraw from the country.
International forces are set to transfer full security responsibility to Afghan forces by a 2014 deadline.
Friday, the United Nations' special representative to Afghanistan, Jan Kubis, said that civilian casualties have gone down by 20 percent in the first four months of this year, compared to the same period in 2011. Kubis would not give exact figures, but said the majority of civilian deaths are caused by insurgent attacks, including suicide bombings.