KABUL  — An Afghan policeman opened fire on Nato forces and Afghan soldiers Monday morning in the fifth apparent attack in a week by Afghan security forces on their international partners. The US-led military coalition says none of its service members were killed.

A Taliban spokesman claimed responsibility for the shooting, which took place in the eastern province of Nangarhar, saying the attacker was a police officer who had been in contact with insurgents before the assault.

A recent rash of “green-on-blue” attacks, in which Afghan security forces or attackers wearing their uniforms turn their guns on the coalition troops training them, has raised worries about a deterioration of trust between the two sides as well as the quality of the Afghan police and soldiers who will take over full security responsibility for fighting the Taliban when most international troops leave by the end of 2014.

 It also raises renewed worry that insurgents may be infiltrating the Afghan army and police despite heightened screening. Nato spokesman Charlie Stadtlander says an initial investigation indicates the attacker was an Afghan police officer, though the man was wearing civilian clothes. He says the shooter escaped. He would not say if any international service members were wounded in the attack, citing coalition policy.

Taliban spokesman Zabiullah Mujahid issued a statement Monday afternoon praising the shooting. He said the police attacker had been “waiting for such an opportunity to attack” international forces.

Mujahid said three Americans died in Monday’s shooting, though the insurgents often exaggerate their assaults’ success.

At least seven American service members have been killed in the past week by either their Afghan counterparts or attackers wearing their uniforms.