Oleksandr Usyk has come through a controversial moment in his world heavyweight title fight with Daniel Dubois to prevail by knockout in the ninth round.

Defending his IBF, WBA and WBO belts against one of his mandatory challengers, Usyk dominated for large periods of the opening four rounds against his British opponent in Wroclaw.

However, in the fifth, Usyk hit the canvas after what was perceived to be a low blow, the Ukrainian taking the majority of the permitted five minutes to recover.

Replays showed that the shot from Dubois was borderline either way, and will inevitably be used by Queensberry Promotions to lead calls for a rematch or lower Usyk's value in a unification showdown with WBC champion Tyson Fury.

Nevertheless, the eventual finish was conclusive, with Usyk flooring Dubois in the final seconds of the eighth round before replicating the feat in the following session.

After what had been a far more competitive fight than many had anticipated, it was a tame ending with Dubois seemingly willing to take a 10 count after what was little more than a jab.

By this point, Dubois had been fading at a time when Usyk had found a second wind after taking punishment in the middle rounds, but the away fighter deserves credit for his performance against one of the pound-for-pound best.

Speaking after the bout, Dubois said that he felt "cheated" out of becoming world champion, while promoter Frank Warren described Luis Pabon's decision to call the pivotal moment in Usyk's favour as "a home decision".

As a mandatory challenger, Dubois is unlikely to gain an immediate rematch, with Usyk expected to square off against IBF mandatory Filip Hrgovic in the New Year.