Eight NATO troops and a contractor have been killed after a former Afghan pilot opened fire after a row at a training centre in Kabul.
The NATO-led International Security Assistance Force (ISAF) confirmed that eight of its troops and one civilian working for the force died following the shooting.
The Pentagon has confirmed that the nine who died were US citizens.
Afghan defence ministry spokesman Mohammad Zahir Azimi said the shootings happened at around 11am (7.30am Irish time) when 'an argument took place between an (Afghan) air force officer and foreign colleagues'.
Colonel Mohammed Bahadur Raeeskhail, the Afghan air force's media relations chief, gave further details.
'There is a conference hall and every morning, Afghan and international staff gather there for a briefing and then they proceed to their daily work,' he told AFP. 'Today at the briefing, this incident happened.'
He identified the 45-year-old gunman as a former pilot re-recruited to the military a few months ago. He had been working as an air force administrator.
'We don't know what exactly happened to cause the shooting and how and by whose bullets these casualties were caused,' added Mr Raeeskhail.
The gunman was shot dead by Afghan soldiers following the killings, which took place at NATO's Air Training Command Afghanistan centre on a site shared by Kabul's military and civilian airports.
The incident was condemned by President Hamid Karzai, who said that five members of the Afghan air force were also wounded. He has promised vowed to launch an inquiry.
The deaths are also likely to raise fresh questions over the massive NATO-led effort to expand and train Afghanistan's military and police so they can take control of security when foreign combat operations end in 2014.
Earlier this month, an Afghan border policeman shot dead two foreign soldiers on a training mission in the northern province of Faryab.
Afghan authorities began tighter vetting of recruits after a renegade soldier killed five British troops in 2009, but there have still been at least 20 people killed in such incidents.
