Former champion boxer James Oyebola, who was shot in the head in a row over smoking at a London bar, died today at 12.39pm.
A police spokesman said Mr Oyebola was pronounced dead by medical staff at New Charing Cross Hospital at 12.39pm.
Detective Chief Inspector Scott Wilson said: "This is now a murder inquiry and we need the people who were in the club that night to come forward as they may have information that could help us piece together what happened last Sunday night.
"James's family are devastated. I would urge anyone with information to come forward to police and assist us in bringing those responsible for murdering James to justice."
Officers from Operation Trident carried out searches of three addresses in Wandsworth today in connection with the investigation.
Mr Oyebola was injured after asking three men to stop smoking in a covered courtyard area at the rear of Chateau 6 in Fulham Road.
Oyebola celebrates victory after his British heavyweight WBC title fight at Cardiff
The 6ft 9ins former British heavyweight champion was shot in the head and leg during the incident in the early hours of Monday morning.
Four shots were fired, but no weapon has been found. No one has been arrested in connection with the incident.
Mr Oyebola, known as Big Bad during his fighting career, arrived at the bar about two hours earlier for a drink with the owner after finishing work at a nearby bar.
The shooting took place 23 days after smoking was banned in pubs, clubs and restaurants in England.
His attackers, described as black and aged between 19 and 25, fled the club on foot - apparently in separate directions.
Chateau 6, formerly the White Hart pub, is close to Chelsea's Stamford Bridge stadium and is a popular haunt for football fans.
Police said there were at least 40 customers in the premises when the shooting took place, many of whom apparently panicked and ran away.
Mr Oyebola, born in Nigeria, won 18 of his 23 fights, and was a bronze medallist at the 1986 Commonwealth Games. After winning the WBC international heavyweight title in 1993, he retired in 1996.