A South African bodybuilder has died in a bizarre manner after attempting a backward somersault during a competition.

In a viral video, Sifiso Lungelo Thabete, dressed only in a black Speedo and socks, can be seem making his way to the gymnasium and whipping at the crowd during the competition held Saturday in South Africa.

With the crowd cheering him on, the 23 year-old attempted to do what looks like a backward somersault.

But he lost his grip and fell on the ground breaking his neck.

He laid motionless for a while before officials ran to his aid.

“The bodybuilding community was shocked and saddened by the tragic news of the death of Sifiso Lungelo Thabete, a bodybuilder from Umlazi in KwaZulu-Natal, at the weekend,” South Africa’s bodybuilding magazine Muscle Evolution published on its website.

The magazine added that said he had “impressed the crowd and the judges with unbelievable muscle size and maturity beyond his age’ in his most recent competition”.

Thabete was rushed to the hospital where he was declared dead.

An inquest docket was opened at Umlazi police station for investigation, the police in South Africa said, News24 reported.

Thabete is said to have a signature backflip he liked to perform when on stage.

"We suspect, because he was wearing socks this time, that he slipped or didn't get enough momentum and landed horribly on his head," Body Building South Africa national executive president Wayne Price told News24.

He won the prestigious junior championship in Johannesburg last month.