The 24-year-old Brunswick East man was stabbed near St Kilda beach late on Wednesday evening after becoming involved in a fight.

The fight between the victim and another man broke out next to the Life Saving Club before moving onto Jacka Boulevard, where he was stabbed by a second member of the group.

He collapsed and was rushed to hospital in a critical condition but died on Thursday morning after his family decided to withdraw life support.

Detective Inspector Andy Stamper said the man of Sudanese background was attacked by an all-male group of African appearance and there was "some level of intoxication" among them.

The group remains unknown but police have viewed CCTV footage of the incident and are urging anyone with mobile or dash-cam vision to come forward.

"It was very busy down there. The chances are that people would have been filming," Det Insp Stamper told reporters on Friday.

It is believed the victim was there by himself and he had never been in trouble with police.

"(He was) just a good young kid, unfortunately, who has for some reason got involved in altercation with another group," Det Insp Stamper said.

It is unclear whether he knew his attackers and what sparked the fatal scuffle.

Det Insp Stamper said the killer, who is believed to have used a knife, would have known he'd delivered a serious blow.

"The person that did this would have potentially had blood on them and known what they did was really serious," he said.

Australian Associated Press