Two US service members have died after an Afghan policeman turned his weapon on American allies in Afghanistan.
The killing in the country's west is the sixth such incident in two weeks.
The shooting happened in the far western province of Farah and the attacker was a member of the Afghan local police, a village defence force being trained by international forces, including US special forces.
Two American service members died before the Afghan attacker was shot and killed. Later in a second attack in southern Afghanistan, troops escaped injury when fired on by another member of the Afghan security forces. The attacker was arrested.
Attacks by Afghan allies on international troops have accelerated this year, killing at least 36 foreign troops and raising questions about the strategy to train Afghans to take over security in 2014.
The deaths came as the Taliban's reclusive leader said that his fighters have infiltrated the Afghan police and army and were successfully killing a rising number of US-led coalition forces.
Mullah Mohammad Omar emailed his eight-page message to news organisations ahead of the Eid al-Fitr holiday marking the end of the Muslim holy month of Ramadan. Omar said Afghan security forces were assisting Taliban fighters who infiltrate their ranks, kill foreign troops and then carry their government-issued weapons back to insurgent camps.
"They are able to (safely) enter bases, offices and intelligence centres of the enemy," he said. "Then, they easily carry out decisive and coordinated attacks, inflicting heavy losses on the enemy."
Attacks where Afghan soldiers or policemen, or militants wearing Afghan uniforms, kill their foreign partners are on the rise, but the coalition claims only 10% of the attacks can be linked to infiltrators.
So far this year, 34 foreign troops have been killed in 27 attacks, according to AP. Last year, 20 international soldiers were killed in 11 such attacks.