Gardaí are investigating a fatal assault that took place in the streets around Grafton Street in Dublin’s city centre in the early hours of Monday.A man aged 21 was found in a serious condition on Grafton Street at 3am after gardaí and emergency services responded to an incident. He was taken to St James’s Hospital where he was pronounced dead a short time later.The fatal assault took place on Clarendon Street, parallel to the main shopping street.The State Pathologist has been informed and a postmortem will be arranged. The scene was preserved for technical examination on Monday morning.Gardaí from Pearse Street Garda station are investigating.They have appealed for witnesses to come forward with information, and for those who may have CCTV or dashcam footage to provide this to gardaí.