Warning: Video contains violence that some readers may find upsetting.

A female police officer was knocked unconscious in a vicious attack in a Manurewa street that was caught on video by a shocked bystander.

The incident took place on the corner of Great South and Station Road on Monday at 12.17pm.

Police confirmed a man, 27, had been arrested following the attack and is due to appear in Counties Manukau District Court today charged with intent to injure.

The man was Tasered after fleeing from police on foot and assaulting the officer.

"The officer involved was knocked unconscious during this incident, and is now off work recovering. She is being well supported by her colleagues," police said in a statement.

A witness captured the attack on camera.

"We would like to thank the community who witnessed this incident for their support and assistance and we appreciate those who came to the aid of our officer."

The witness who filmed the video told the Herald he was waiting at the traffic lights when he saw police chasing after the man who was "in an agitated state".

As the officers surrounded the man on foot, he approached a female officer and punched her in the face.

She collapsed on the street clutching her face and was tended to by shocked members of the public.

Members of the public went to help the stricken officer, who was lying prone in the middle of the street.

The witness told the Herald she saw blood coming from both her eyes and nose.

As the alleged attacker then tried to flee he was Tasered by another officer.

However the Taser appeared to have little impact and he can be seen walking away with the barbs still lodged in his back.