Police are seeking the man in the blue shirt, who allegedly knocked a man out with an unprovoked punch.

A man who was punched in the head in a surprise assault outside an Auckland bar suffered a brain bleed and spent three days in an induced coma.

Police are seeking the man responsible for the punch, as well as a man who hit the unconscious victim in the face, outside the Weighbridge Bar in Papatoetoe on Sunday, October 13, about 2.20am.

CCTV footage of the incident aired on Police 10/7 on Thursday shows the victim standing outside the bar on the corner of Great South Rd and East Tamaki Rd, where he had been with his cousins for several hours, during which he encountered the first suspect.

Police said that at one point, the victim left the bar and was denied re-entry due to being intoxicated. While the victim was chatting with the bouncer, the first suspect who was lurking to his right threw a punch to the victim's head, knocking him out.

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The victim also hit his head on the pavement as he fell, and was hit by another man while he lay unconscious. Neither suspect were known to the victim.

NZ Police A second man, wearing a Bulldogs rugby league jersey, hit the unconscious man in the face.

Both suspects snuck away as emergency services began to arrive, and left the scene together in a silver Honda Odyssey.

The victim suffered a brain bleed and spent three days in hospital in an induced coma. He also had to take six weeks off work and had been having vision and balance problems.

Counties Manukau police said there was "no aggro and nothing to suggest that violence would ensue" prior to the attack.

NZ Police The two men are understood to have left the scene in this silver Honda Odyssey type vehicle.

"He [the victim] was not being violent, the bouncer had everything under control. There was no need for anyone to step in and throw this cowardly punch," Detective Constable Andy Wright said.

"He's on a long road to recovery."

The man who threw the first punch had hair worn to his shoulders and was wearing a dark blue T-shirt and black trousers. The man who hit the unconscious victim was wearing a black Raiders baseball cap, Bulldogs rugby league jersey and a Fila satchel over his chest.

Witnesses of the incident said the men were speaking to each other in Tongan.

Police request anyone who witnessed the assault or recognises the suspects phone 0800 107 4636.