New Zealand's elite SAS troops have taken part in a secret mission to take out the Taleban insurgents responsible for the death of a New Zealand soldier last year - but the Government is denying it was a revenge mission.

Lieutenant Tim O'Donnell was killed in August in an ambush in a mountainous region of Bamiyan province in Afghanistan - the first New Zealand soldier in a decade to die in combat. A counterattack involving the SAS took place two weeks later. Last night, the Defence Force said nine insurgents were killed, not 12 as earlier reported.

Defence Minister Wayne Mapp said it was not a revenge killing but "to secure the area".

"It is a war and military operations do take place," Dr Mapp told One News.

Lieutenant O'Donnell died on August 4 while on patrol in northeast Bamiyan. The Taleban fighters who attacked the convoy had come from neighbouring Baghlan province.

On August 22, the International Security Assistance Force (ISAF), as the Nato force is known, led an early-morning raid in Talah wa Barfak District, Baghlan.

Dr Mapp confirmed New Zealand forces were part of the mission, but it is not clear how many were involved or whether they shot any insurgents.

"We have special forces to be able to undertake military operations - that is part of their overall remit."

The district's governor initially said there were eight civilian casualties, and a Nato investigation later revealed a malfunctioning gunsight on a coalition helicopter that had resulted in errant shots hitting a building. The building was struck mistakenly, but was previously used as base of insurgent operations.

US Air Force Brigadier General Timothy M. Zadalis said at the time that the coalition regretted "any possible civilian loss of life or injury".

Dr Mapp said investigations had found that no civilians were killed in the strike. It was not unusual for the SAS to move out of Kabul, where they were usually based.

"It is in the remit of the special forces to be able to undertake operations at the direction of ISAF and Nato, and in this case particularly to protect our people."

Lieutenant O'Donnell was part of the provincial reconstruction team of about 140 New Zealand troops who do aid work and military patrols in Bamiyan province. The team is due to withdraw by 2014.

Recently, New Zealand forces in Bamiyan were beefed up with five extra light armoured vehicles and more infantry.

"The northeast is the most demanding part of our area of operations and requires a higher level of capability," the Commander of Joint Forces, Air Vice Marshal Peter Stockwell, said last week. "This area of the province was where Lieutenant Tim O'Donnell was killed last year, and it is where we have most often come into contact with armed insurgents."

Green Party defence spokesman Keith Locke said the SAS should not be involved in the war, regardless of whether it was in Kabul or Baghlan.

"We would rather that they weren't there. This ongoing, apparently unwinnable war is not one we should be involved in."

The 70 SAS troops were due to pull out of Afghanistan last month, but the Government approved a smaller group staying on for a further year.