A robbery on a Hamilton street has left a man with serious head injuries.

The 18-year-old Indian man was admitted to Waikato Hospital, after being attacked by three men on Wairere Drive at around 9.30 last night.

Police say he was knocked unconscious in the assault.

They are calling for any witnesses, to help identify the offenders, who are described as Maori or Polynesian.

Police say the eldest is around 22-years-old and of a short, chubby build, with a moustache and short hair.

The second offender is believed to be around 16-years-old, of a skinny build, with tattooed writing on his forearm, while the third is believed to be under 16-years-old.

The trio were last seen walking on Wairere Drive toward Old Farm Road.