Police are hunting five men after a woman was sexually assaulted at sporting field in Lismore on the New South Wales north coast.

The 30-year-old was walking home from a local hotel when she was confronted by a group of men near a toilet block at Gloria Mortimer Oval about 1:30am on Friday.

Police say she was held against her will and sexually assaulted by the group.

The woman went home and told relatives about the attack and was taken to hospital for treatment.

Police set up a crime scene at the oval which has been examined by forensic officers.

The five men have only been described as being of Aboriginal or Torres Strait Islander appearance.

Detectives are appealing for any witnesses to contact them.