It's happened just days after a 16 year old boy was also stabbed in the town.
Norwich: Appeal Over New Year Assault
Detectives are appealing for help to trace a man who went to the aid of a woman who is believed to have been assaulted in Norwich.
The incident is believed to have taken place in a silver car sometime between 6am and 7am on New Years Day in the area of St Faiths Lane and Cathedral Street.
The 30-year-old woman was assaulted by a man who tried to touch her in her chest and groin area.
As she attempted to struggle free a man, described as being white, aged in his 30s with long brown hair in a ponytail and wearing a long leather jacket, went to her aid and she managed to get away.
Officers are particularly keen to speak to the man as they believe he may have vital information relating to what happened.
Witnesses are asked to contact Det Con Carly Jermy at Norfolk Constabulary on 101 or Crimestoppers anonymously on 0800 555 111.
Five people have been arrested in connection with a stabbing in Ipswich over the weekend.
More Venues Shut Early On Sunday After Low-Level Disorder
The family of an 83 year old man murdered in East Harling, have thanked Norfolk Police.
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