The second shooting of Western troops by one of their Afghan counterparts this month has highlighted the potential hazards of a push to speedily expand Afghanistan's army and police forces in the next few years.
On Tuesday, an Afghan army sergeant opened fire at an army base in northern Afghanistan, killing two American civilian trainers before being shot dead. That followed an attack in the south on July 13, when a soldier killed three British troopers, including the company commander, with gunfire and a rocket-propelled grenade in the dead of night.
Military commanders have described the two attacks as isolated events, and it is indeed rare for an Afghan soldier to turn on NATO forces. Still, they feed on larger doubts about the ongoing massive recruiting among a largely illiterate population — many of whom are used to holding a gun but not to rigid military discipline.
The concerns include possible infiltration by the Taliban and the professionalism of the forces at a time when NATO hopes to expand the Afghan army from 85,000 troops in 2009 to 134,000 by October 2011. The eventual goal is to turn over the responsibility for nationwide security to Afghan forces by 2014 so that foreign troops can go home.
NATO has six large training sites across the country, and there are about 20,000 soldiers and about 6,500 police undergoing training at any one time, said Col. Stuart Cowen, a spokesman for the NATO training mission.
"We regard what happened yesterday as a tragic and isolated incident and we are looking at the training, and taking prudent precautions to make sure that doesn't happen again on our firing ranges," Cowen said Wednesday.
He said that there is a strict program for vetting recruits before enlistment, including drug tests, physical exams and a check against a database of known insurgents. Potential recruits also have to get their community elders to vouch for them in a written letter.
"People do fail selection," he said, specifying that about 7 percent of applicants do not make the cut.
Even so, there are Afghan soldiers who light up hashish or marijuana during patrols and Afghan police officers who use checkpoints mainly to shake down motorists for bribes. NATO is trying to get troops and police through regular retraining programs, but this process moves slowly.
Maj. Gen. Richard Mills, the commander of NATO forces in southwestern Afghanistan, said that while Afghan security forces have greatly improved, they've had trouble finding infantry soldiers with the skills to promote up to officer level.
"They need to work on their junior leadership," Mills said.
The shooter in Tuesday's attack was a "group leader" — an Afghan soldier selected to train other soldiers on the base, Defense Ministry spokesman Gen. Mohammad Zahir Azimi said. U.S. Brig. Gen. Gary Patton, deputy commander of the training mission, said the shooter was a sergeant.
The shooting started with an argument during a weapons-training exercise at a firing range on an Afghan army base outside Mazar-e-Sharif. The Afghan soldier turned his weapon on the American civilian trainers and shot two of them before being gunned down, the Afghan Defense Ministry said. Another Afghan soldier was killed in the crossfire.
NATO suspended training throughout the country after the shooting but resumed full operations Wednesday, Patton said. It was unclear what the argument was about, and the Afghan government and NATO have launched a joint investigation.
The attack on the British soldiers earlier this month in Helmand province was also puzzling — but for different reasons.
The Afghan soldier, who fled after the attack, belongs to a minority ethnic group largely supportive of NATO troops and bitterly opposed to the Taliban.
But the Taliban claimed the attacker was a militant sympathizer taken in by the insurgents after the assault.
And a man claiming to be the fugitive Afghan soldier has conducted telephone interviews with several Western news organizations with the help of the Taliban. He told The Associated Press that he turned on coalition soldiers because they killed "innocent people" and used search dogs too close to Afghan women, an indignity.
A NATO official said at least some of the information provided by the man was inconsistent with what is known about the attack.
The killings were a blow to Britain, where public support is ebbing for the war. It was the second time in eight months that a member of the Afghan security forces attacked British troops. In November, an Afghan policeman killed five British soldiers in the south.