The 24-year-old man was found unconscious on Bold Street in the city centre.
Paramedics attended the victim and were called at approximately 1am.
The 24-year-old was treated and then taken to hospital due to the severity of his injuries.
The victim is from Northern Ireland and had been visiting family in the city, detective chief inspector Paul Parry revealed.
He had also been with three friends when it is believed before they were assaulted on Hanover street.
The police have called on any taxi drivers from the nearby Hackney cab rank on Hanover Street if they have information or dashcam footage.
Police have now launched a full investigation while the man is being treated for serious head injuries.
This is a breaking news story, more to follow…