Dyfed Powys Police are investigating an assault that happened in Llanelli between 11pm and midnight on Saturday.
A 12 year old girl received minor injuries in the incident.
The suspect is described as a white man aged 30-35 with short spiky dark hair. He was wearing a Scarlets rugby top and light grey tracksuit bottoms.
Anyone with information should contact Llanelli CID.
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Feeling humid with heavy showers and thunderstorms moving north overnight into Sunday.
Four people, including three children, were taken to hospital to be checked for smoke inhalation.
Heavy rain and thunderstorms will affect many parts of Wales this weekend - particularly during Saturday evening.