An Afghan soldier killed a U.S. service member and wounded two Italian soldiers when he opened fire on foreign troops at an army base in western Afghanistan on Tuesday, a senior Afghan army officer said, Reuters reported.
The shooting is the latest in a string of such incidents, at a time when Western countries are pouring resources into training Afghan soldiers and police to fight the Taliban insurgency.
"The soldier opened fire on the two Italians and one American in a joint Afghan and foreign base," General Khair Mohammad Khawari, a senior officer in western Afghanistan, told Reuters.
"Two Italian soldiers were wounded, one American soldier was killed," Khawari said, adding that the Afghan soldier had been wounded when NATO forces returned fire and was now in hospital.
The assailant comes from an area north of the Afghan capital Kabul and is thought to have mental health problems, Khawari added. The Taliban traditionally had less of a hold in northern Afghanistan but have expanded their reach across the country.
A spokesman for NATO-led forces said a U.S. service member had died following a shooting incident in western Afghanistan. Foreign and Afghan forces were investigating the incident, he said, but declined to give any more details.
Italian Defense Ministry officials said the attack, which was deliberate and not a case of friendly fire, occurred during a routine supply operation.
One Italian was lightly wounded in the thigh and the other in the hand and leg but both have returned to their duties.
Violence in Afghanistan has reached its highest levels in the eight-year war and 2009 has been the bloodiest year for foreign troops. More than twice as many Americans have died in Afghanistan this year than in 2008.
U.S. President Barack Obama is sending in 30,000 extra troops as part of his new war strategy, to try to turn the tide. Other NATO countries are sending some 7,000 more.
But Washington's plan also calls for U.S. troop levels to be scaled down from 2011 as they gradually hand over security to the Afghans and the White House has said the United States will not be in Afghanistan in eight or nine years time.
Attacks by Afghan soldiers on their foreign mentors highlight the sometimes testy relations between the two and have prompted public debate in the West about the war and concern over the safety of troops embroiled in an increasingly unpopular conflict.
Last month, an Afghan policeman killed five British soldiers at a military compound in southern Helmand province.
The Taliban said he was one of their fighters who had infiltrated the force and the incident prompted Britain to improve its vetting procedure for Afghan police.
Four U.S. troops were killed and three wounded by Afghan soldiers in two other incidents earlier this year, one in the northeast and one just south of Kabul.