Oleksandr Usyk has vacated the IBF heavyweight championship just five weeks after becoming undisputed world heavyweight champion with his win over Tyson Fury.

The Ukrainian handed Fury his first professional defeat via a split decision last month to unify the WBC belt with his WBA, WBO and IBF titles.

The fighters are set to face off in a rematch in December and Usyk had requested he keep the IBF belt to make that contest another undisputed bout.

However, the IBF's rules dictated that Usyk had to be stripped of the title if he did not face mandatory challenger Daniel Dubois next.

View this post on Instagram

A post shared by Usyk. The Cat. Oleksandr (@usykaa)

Dubois is expected to face fellow Brit Anthony Joshua at Wembley Stadium on September 21, and that fight is now likely to be for the IBF championship.

Addressing Joshua and Dubois in an Instagram post, Usyk wrote: "The IBF belt is my present for you.

"Your friend, the undisputed heavyweight champion of the world, Oleksandr Usyk."

Usyk was the first undisputed heavyweight champion since the turn of the century, with Lennox Lewis last achieving the feat in the three-belt era in 1999.