A "small number" of the New Zealand SAS team in Afghanistan were involved in response to an attack which killed at least 13 people and wounded more than 70 in the Afghanistan capital, Kabul, Prime Minister John Key said today.

A team of militants launched the assault in Pashtunistan Square, an area that holds the Ministry of Justice, the Central Bank and the palace of President Hamid Karzai, about 9.30am local time, with two men detonating suicide bombs.

Mr Key said the soldiers were uninjured and it wasn't known if they fired at the insurgents.

Mr Key said their were no plans to scale back New Zealand's involvement in Afghanistan, despite the incident.

Afghan officials said three soldiers and two civilians - including a child - were killed, and at least 71 people were wounded. Seven militants died in the attack, five were gunned down and two killed themselves.

The New York Times reported a small group of commandos from New Zealand were the only Western soldiers on the scene.

The New Zealand Defence Force is refusing to confirm or deny whether the SAS were involved in the fighting.

Major Kristian Dunne said the military did not comment on SAS operations.

He said the five army personnel in Afghanistan as part of the International Security Assistance Force (ISAF) were at a military base at the time.

Major Dunn said the base was locked down and they were not involved.

New Zealand Defence Force spokesman Commander Shaun Fogarty earlier said no New Zealanders were injured in the attack.