A 32-year-old man was attacked in a park in Thetford ater being approached by a group of up to six people.
The victim suffered a head injury during the assault in Castle Park on Friday between 10pm and 11pm.
He was with a friend when he was approached by the group and hit a number of times causing a large cut and swelling to his head.
Officers want to speak to anyone who may have seen the incident or has information about it.
They should contact PC Ian Hinchliffe at Thetford Police Station on 101 or call Crimestoppers anonymously on 0800 555 111.