The man attacked in Eastbourne on Tuesday night remains in a coma with life-threatening injuries.
The 25-year-old, who is from Madeira, is being treated at the Royal Sussex County Hospital in Brighton.
He was badly beaten in an incident in St James Road off Seaside and suffered serious head injuries.
According to the Diário de Notícias da Madeira, a local paper in Portugal, the man is from the parish of Curral das Freiras (Câmara de Lobos).
The newspaper reports the man and his girlfriend, who is also from Madeira, were followed to a supermarket and he was “suddenly attacked by a group of around 15 people”.
A friend of the couple told the newspaper, “He desperately shouted for his partner to run away and ask for help.”
Emergency services were called and firefighters who were passing by rushed to help.
Police have launched a major investigation.
Detective Inspector Neil Bates said, “This was a vicious attack in broad daylight at a time when there were a lot of people around. We want to hear from anyone who may have witnessed the incident or any events leading up to it. We do have a number of suspects who are being actively sought, but I would urge anyone with information, no matter how incidental they may think that to be, to contact us as soon as possible.
“Please report online or call 101 quoting Operation Netherby.”