Hamilton police and forensic experts are working to identify a man who was found dead in suspicious circumstances in central Hamilton early this morning.

A homicide investigation was launched after a Caucasian man believed to be in his late 50s or early 60s was found dead by a street sweeper who found the man's body off London St, near some public toilets at about 6am, Detective Inspector Lance Burdett said.

"The man was found unresponsive, lying on his back with head injuries," Mr Burdett said.

The man's death was being treated as suspicious and his injuries did not appear to be as a result of a fall."

Police are appealing for any sightings of the man last night in or around the area he was found.

They would also like to speak to anyone who may have seen or heard a fight involving a man matching the victim's description.

Police hoped a scene examination and an area canvas which commenced this morning would provide answers, Mr Burdett said.

The scene examination was being carried out in conjunction with Environmental Science and Research (ESR) forensic experts, he said.

Police hoped to be able to remove the body from the scene later today and a post-mortem would be carried out in Auckland to determine a cause of death.

There was no evidence to link the death to the All Blacks test match against Wales in the city overnight, Mr Burdett said.

The man is described as a male Caucasian with short grey hair, aged in his late 50s to early 60s who was wearing light tan pants, a light blue jacket with woollen sleeve cuffs, a dark brown jersey under his jacket and brown slippers.

Police preferred to speak to any witnesses directly but anonymous calls could be made to Crimestoppers.