Three men entered the front garden of a Norwich property and assaulted a man in his 30s.
Police said the attack happened at Wakefield Road, in the Earlham area of the city, on Friday, July 27 at around 7.15pm.
Two men from the Norwich area - one in his 20s and another in his 40s - were arrested in connection with the incident.
But police said they have since been released under investigation while enquiries continue.
Anyone with information should contact PC Martin Bentley at Norwich Police Station on 101.
Alternatively, contact the independent charity Crimestoppers anonymously on 0800 555 111 or via their anonymous online form at crimestoppers-uk.org.
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