A young woman was treated in hospital for facial injuries after an assault in Ashington on Saturday night.
The incident happened in fields close to Rectory Lane and Blakiston Close between 11pm and 11.20pm.
PC David Slade said: “This was a totally unprovoked and nasty assault.
“Although a man has been arrested, I am appealing for any witnesses who may have heard or seen the victim in distress.”
A 23-year-old man from Ashington was arrested on suspicion of causing actual bodily harm.
He was questioned and released on police bail until Wednesday 31 July.
Anyone who witnessed the incident call 101 quoting serial 1717 of 22/6, or call Crimestoppers on 0800 555 111.