Two US civilians and an Afghan soldier were killed on last night in a shooting by another Afghan soldier at a weapons training area in the north of the country, the US military said.
Afghan and NATO forces were still investigating the circumstances around the incident, which also resulted in the death of the suspected shooter and the wounding of a foreign service member and an Afghan soldier, it said in a statement.
Earlier, provincial sources said a renegade Afghan, serving with government security forces, had killed two members of the NATO-led force.
The incident occurred at a military training camp near to the northern city of Mazar-I Sharif, the US military said, adding the suspect was "thought to be an Afghan army trainer."
"A joint ... investigation is under way to determine the circumstances surrounding the shooting by an Afghan army soldier that led to the death and injury of several individuals," it said in a statement.
The incident comes on a day a major international conference in Kabul agreed that Afghanistan should have the leading role in its own security across the country by 2014 and in some areas by the end of this year.
It also comes a week after a renegade soldier killed three members of a British Gurkha regiment, including a major, before escaping.
Afghan soldiers are expected to take more responsibility for the country's security as the 150,000-strong, US-dominated force starts a gradual withdrawal from next year, and NATO commanders are quick to play up their role in joint operations.
The rapid creation of a national army and police force since the Taliban's ousting in 2001 and following decades of war has seen tens of thousands of Afghans join the security services, and there are fears Taliban insurgents - or sympathisers at least - may also have signed up.
Reuters