Men wearing Afghan police uniforms shot dead two Nato service members in southern Afghanistan, authorities said, the latest in a string of attacks on international troops by Afghan security forces or militants disguised as police.
Two other coalition service members also died in Afghanistan, one in an insurgent attack and another of non-battle related injuries.
There were conflicting reports about the shooting in Helmand province.
Fareed Ahmad, a spokesman for the Helmand provincial police, said two Afghan policemen opened fire on coalition troops at 3pm at a joint Afghan-coalition compound, killing two coalition troops. He said a third Afghan policemen fired at the attackers, killing one and wounding the other, who escaped.
The attackers had been members of the Afghan National Police for one year and were from Nangarhar province in eastern Afghanistan, according to Ahmad
Nato said it was aware of the Afghan statements, but that operational reports indicated that the assailants were insurgents dressed in police uniforms, not official members of the police force. The coalition also said that one attacker was killed and the second was being pursued.
It said the shooting was still being investigated.
A man wearing an Afghan army uniform shot dead a US soldier on Friday in eastern Afghanistan. That shooting was the 15th incident this year in which Afghan soldiers or insurgents disguised in military uniforms have turned their weapons on foreign troops, according to Nato.
Also, a roadside bomb killed a third Nato service member, while a fourth died of non-battle related injuries. All four deaths occurred in the south, where much of the fighting in the more than 10-year conflict has been concentrated, the alliance said in a statement.
Separately, four Afghan police officers were killed in the north-western province of Badghis when their vehicle struck a roadside bomb in Qadis district, said the provincial governor's spokesman, Sharafudin Majedi.