The insurgents who killed two New Zealand soldiers in Afghanistan are a new, sophisticated group the Defence Force believes were sent to help target Kiwi troops after other groups failed to gain traction.

Chief of Defence Force Lieutenant General Rhys Jones said the attack happened in the North East of the Bamiyan province - an area where historically, there were a lot of issues.

That was in part because the neighbouring area was not controlled by coalition forces and provided an entry point.

Because of the steep terrain, New Zealand forces were unable to follow the insurgent troops into the mountains, he said.

The main highway through the area - where the local forces faced the attack which led to the Kiwis going in to help - was a well-known problem area.

"That's there traditional activity zone. It's a very vulnerable road," Jones said.

However, usually the attacks were done with IEDs.

The new group - thought to be from the South and who the Defence Force had been tracking "for some time" - had been using IEDs frequently in recent months. They were better funded and had a bomb maker that was "quite proficient," Jones said.

NZDF forces were able to handle the IEDs they discovered and disarmed them, but last night's attack was a different circumstance altogether, he said. It was ground-fire based, not an IED attack.

"I can remain confident our guys were well prepared for it... but the reality is that this is a battle zone."

The enemy would learn and improve just like the Kiwi troops would, he said.

Prime Minister John Key said the group was more "sophisticated" than previous groups. They were also better equipped.

He said NZDF were aware of their presence and were working actively against them.

Asked if he thought whether New Zealand troops now needed to stay longer to combat the new group, Key said no.

"Staying longer wouldn't achieve more. They tragedy is that you will get insurgent groups that will continue to be active after the troops have gone."

However, he did not think it meant the troops should pull out earlier.

"I don't think terrible loss we've suffered overnight means we should leave earlier. We should continue on track."

Exiting the troops was a huge logistical exercise, he said.

- © Fairfax NZ News