Hertfordshire Police officers are asking two witnesses to come forward following an assault in Hemel Hempstead.
The incident happened on June 1, around 3pm in the underpass from Jarman Park towards the town centre.
A woman in her twenties was walking when four teenage boys approached her.
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Police say they blocked her path and when challenged, one of the boys began punching her and she was verbally assaulted.
PC Rebecca Maddock, who is investigating, said: “This was a frightening ordeal for the victim and we have been doing everything we can to find those responsible.”
The police inquiries have found that two members of the public, a male and a female, are believed to have witnessed what happened, with the male reportedly chasing the boys away.
PC Maddock said: “If this was you, please get in touch straight away as you may be able to help us progress our inquiries. I am also keen to hear from anyone else who believes they have information.”
The first teen is described as being under 16 years old, possibly mixed race with afro-style hair.
The second male is described as white and under 16.
The third male is described as white and aged 16 or 17 years old.
He had a bike with him and was wearing a black baseball cap, dark trousers and a black hooded jacket with a white logo down the sleeve (possible Nike).
The fourth male is described as white with brown, curly hair and of a quite small build.
He was wearing a red jacket and carrying alcohol.
Anyone with information is asked to get in touch with PC Maddock here or by calling the non-emergency number 101 quoting crime reference 41/43573/22.