Police have revealed that the man assaulted on Upper Parliament Street is in a “serious” condition at the Queens Medical Centre.
Part of the pavement on Upper Parliament was cordoned of on Wednesday as well as Trinity Square and Kings Walk forcing businesses in the area to close.
A patch of blood on the pavement can be seen near the entrance to Kings Walk.
A police spokesperson said they have made no arrests at this stage and that the cordons will remain in place for most of the day.
Anyone with information should call 101, quoting incident number 63 of April 15, or Crimestoppers on 0800 555 111.
The investigation continues.