(CBS/AP) KABUL, Afghanistan - 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 U.S.-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.
The coalition has recorded 27 so-called green-on-blue attacks so far this year, resulting in 38 deaths - a dramatic rise from previous years.
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.
The Taliban traditionally steps up attacks in August, but the militant group's claimed success in recruiting rogue forces from the ranks of the Afghan army and police to turn on their Western allies, with whom they work and live very closely as ISAF ramps up its planned transition of security to Afghan forces, has fostered a lack of trust.
At least seven American service members have been killed in the past week by either their Afghan counterparts or attackers wearing their uniforms.
Coalition officials say a few rogue policemen and soldiers should not taint the overall integrity of the Afghan security forces and that the attacks have not impeded plans to hand over security to Afghan forces, which will be 352,000 strong in a few months. But there is growing unease between international troops and their Afghan partners and that's something Taliban insurgents are happy to exploit.
While the Taliban often claim they have infiltrated the Afghan security forces and are carrying out these attacks, CBS News reporter John Bentleythat a U.S. Defense Department report maintains the attacks are not carried out by insurgents.
"Investigations have determined that a large majority of green-on-blue attacks are not attributable to insurgent infiltration of the ANSF (Afghan National Security Forces), but are due to isolated personal grievances against coalition personnel," the report said.
The Afghan security forces have established an eight-point vetting process. ISAF spokesman Brig. Gen. Gunter Katz explained that recruits require two letters from local elders as a character reference as well as biometric, medical and drugs checks, but ISAF is still working with the Afghan forces to improve this process.
Nonetheless, early in 2012, top U.S. commander Gen. John Allen ordered American units toto watch over fellow troops, even as they sleep, at joint U.S.-Afghan bases and on joint operations involving live fire - a direct response to the mounting green-on-blue attacks.
Last year, a U.S. Army team led by a behavioral scientist produced a 70-page survey that revealed both Afghan and American soldiers hold disturbingly negative perceptions of the other.
According to the survey, many Afghan security personnel found U.S. troops "extremely arrogant, bullying and unwilling to listen to their advice" and sometimes lacking concern about Afghans' safety in combat. They accused the Americans of ignoring female privacy and using denigrating names for Afghans.
American troops, in turn, often accused Afghan troops and police of "pervasive illicit drug use, massive thievery, personal instability, dishonesty, no integrity," the survey said.
U.S. military officials have downplayed that survey.