Welterweight champion Kamaru Usman ground out a decision victory over Jorge Masvidal to keep his belt, and Alexander Volkanovski retained his featherweight title with a split decision victory over Max Holloway at the UFC 251 event in Abu Dhabi on Sunday.

With Masvidal taking the title fight on six days' notice after Gilbert Burns was forced to pull out after testing positive for the new coronavirus, Usman used his superior wrestling and clinch work to wear down the challenger over five rounds.

The 33-year-old ripped vicious hooks to the body against the cage and smothered Masvidal on the ground, sapping the challenger's energy en route to a convincing win.

"All these guys, they're preparing for one guy, and that's me, at the top of the mountain, and I had to make a mental shift," Usman said after the fight. Masvidal "is tough, and he showed it out there."

In the co-main event Australian Volkanovski, who won the featherweight belt from Holloway via unanimous decision in December 2019, found himself behind early on, after he was knocked down at the end of each of the first two rounds.

The former semi-professional rugby league player dug deep, relying more on his wrestling and doing just enough over the final three rounds to edge out the Hawaiian on the judges' scorecards and remain unbeaten in the UFC.

In the card's other title fight, Russia's Petr Yan scored a brutal technical knockout over Brazilian Jose Aldo to claim the bantamweight title left vacant by the retirement of previous champion Henry Cejudo in May.

Dropping down a weight class, former featherweight champ Aldo held his own but wilted in the fourth round, and the Russian dominated him with ground strikes in the fifth until the referee waved the fight off, declaring Yan the winner by TKO.