A 19-year-old woman has been taken to hospital with what are described as serious injuries. She is in a critical condition.
A 21-year-old man has been arrested in connection with the incident and is currently in police custody.
Graig Avenue will remain closed to allow police to carry out a thorough investigation and officers will remain at scene carrying out house to house enquiries and providing support to the community.
Police are appealing for any witnesses who were in the Graig Avenue area between 5-7pm on April 13th to contact the Incident Room in Llanelli immediately with any information that could help the investigation by calling 101.