Rahmat Gul, Associated Press
An Afghan newly graduated border police officer, right, shakes hand with his commander, as he receives his certification during a graduation ceremony at the border police headquarter in Jalalabad, Nangarhar province east of Kabul, Afghanistan, Tuesday, Jan. 31, 2012. Over 40 border police officers graduated after receiving 10 weeks of training in Jalalabad. More than half of Afghans polled see the national police as corrupt, but the force's overall reputation is improving as international forces prepare to hand over security responsibility by the end of 2014, a U.N. survey indicated Tuesday.

KABUL, Afghanistan — An Afghan soldier shot and killed a NATO service member in southern Afghanistan, officials said Wednesday, the latest in a string of similar attacks that has raised concerns about relations between Afghan troops and foreign allies.

International forces and the Afghan army disagreed on exactly what happened in the killing.

Lt. Col. Jimmie Cummings, a spokesman for the international military force, said Afghan soldiers detained the gunman after he attacked NATO troops Tuesday night. The coalition gave no other details.

Afghan National Army commander Sayed Malluk confirmed the shooting, which he said happened during a night patrol in Helmand province's Marjah district. But he said the Afghan soldier, who has been in the army for more than two years, told investigators the shooting was an accident.

It was the sixth report since Dec. 26 of an Afghan soldier — or an insurgent posing as one — turning his weapon on the international troops working to train the Afghan security forces.

After an Afghan soldier killed four French soldiers on Jan. 20, French President Nicolas Sarkozy announced that France would speed up the exit of its troops from Afghanistan and that it would ask NATO to hand over all combat operations to Afghan forces in 2013 instead of by the end of 2014.

Sarkozy at the time said the attacker was a Taliban infiltrator, but Afghan and NATO investigators have said it was too early to know his motivation.

The rising number of attacks by supposed friendly Afghan forces has prompted speculation that Taliban insurgents or sympathizers may be infiltrating national army and police as they rapidly expand to meet a 2014 target for Afghan forces to take over security and most international troops to leave.

There have been at least 35 attacks on international troops since 2007 by Afghan soldiers, police or insurgents wearing their uniforms, according to a tally by The Associated Press. The number rose sharply last year to 17, up from six in 2010.

But NATO spokesman Cummings said Wednesday the rising number of attacks doesn't point to any pattern.

"We feel they're isolated cases," he said. "There's no indication these incidents are linked or part of any coordinated effort."

Cummings said that the 130,000-strong international force works daily with more than 300,000 Afghan security personnel, mostly without problems. He said that NATO is satisfied with Afghanistan's vetting process for army recruits.

Tuesday's attack brought to 34 the number of international troops killed in Afghanistan this year.