A 30-year-old man suffered a broken jaw after he was assaulted in Fleur de Lis.
The attack happened outside the Valley Tavern pub and cafe on High Street, sometime between 11pm and 11.30pm on Wednesday, August 5.
The attacker is described as a man in his early to mid-twenties.
A 21-year-old man from Newport has been arrested on suspicion of grievous bodily harm and has been released under investigation.
Gwent Police is investigating the incident and launched an appeal for information on Tuesday (August 18).
Anyone with information can contact Gwent Police on 101, quoting reference 2000282041. Gwent Police can also be contacted through direct message on Facebook and Twitter.
Alternatively, Crimestoppers can be contacted anonymously on 0800 555 111.
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