Prime Minister John Key says it is impossible to rule out future casualties among SAS troops sent to Afghanistan.
Mr Key on Monday confirmed that members of the Special Air Services came under fire after a car bomb blast in Kabul, in line with the Government's new policy on discussing the elite unit's activities.
He says up to 15 members of the SAS were accompanying an Afghan unit in response to the explosion and the occupation of a building by a group of insurgents on Friday.
Mr Key says during the incident, some members of the SAS were fired upon by insurgents and they returned fire.
The insurgents then blew themselves up before they could be apprehended by Afghan security forces.
No New Zealanders were injured, but eight civilians were killed in the initial bomb blast and about eight insurgents died, Mr Key says.
He says as far as he is aware, it is the first time SAS weapons have been fired during combat on this deployment, but there could be other occasions.
Mr Key says the Government has done all it can to make sure the troops have all the support they need.
Defence specialist Ron Smith says it is a good thing the Government is being more open about SAS activities in Afghanistan.
However, Dr Smith, co-director of Waikato University's international relations and security studies programme co-director, says it is important not to get "carried away" and prejudicing their security.
He says international media attention on the SAS in Kabul has obliged the Government to be more open.
New Zealand SAS Association president David Moloney says it is very important individuals are not identified.
Mr Moloney says while it is unreasonable to expect operations such as that in Kabul to be kept quiet forever, the association's previous and serving members are probably uncomfortable with details being released.