Oleksandr Usyk retained the WBC, IBF and WBA heavyweight titles after defeating British challenger Daniel Dubois via TKO at the Tarczynski Arena on Sunday morning.

Fighting in front of a partisan crowd of 40,000, the 26-year-old Ukrainian dropped Dubois late in the eighth round and finished the job in the next stanza to improve his unbeaten record to 21-0.

However, Usyk’s triumph was shrouded in controversy. Dubois caught Usyk in the stomach with what was considered a low blow in the fifth round, forcing a lengthy stoppage and causing the champion immense discomfort.

The incident sparked a debate over whether the shot was legal and Usyk should have been counted.

BOX | SUN 27 AUGRA: In a title fight, Oleksandr Usyk will defend his heavyweight belts against Londoner Daniel Dubois at the Tarczynski Arena, Wroclaw, Poland. MAIN EVENT ORDER AT KAYO SPORTS >

“It was never a low blow and Usyk should have been counted out,” said TNT Sports’ Carl Frampton.

“Daniel Dubois should be world champion.”

Dubois was left angry after the fight, stating, “I don’t think it was a low blow. They cheated me out of winning tonight. That was a win.”

When the footage was shown on the big screens in the arena, Dubois raged: “How low is that? How low is that? That’s my question. Look at it! Play it again!”

Legendary British boxing promoter Frank Warren continued: “It wasn’t a low blow… I like Usyk, but it was a complete hometown decision. He won this fight because he was unable to continue and was given a few minutes to recover from a legitimate shot.

“It’s complete nonsense. How long has he been recovering? The governing bodies will have to look at that and order a rematch. We’ll order an appeal of what happened here.”

“Justice must be served… That was bulls***!”

After the fight, Usyk called out WBC heavyweight champion Tsyon Fury.

“I’m ready tomorrow.” Listen, I’m ready. Next fight I’m ready to fight Tyson Fury. Will Tyson Fury? I have no idea,” he said.

“I can’t wait to see my kids and be back home. I have been training for a long time. I’m a little tired.”

Oleksandr Usyk vs. Daniel Dubois Undercard

Oleksandr Usyk def. Daniel Dubois via ninth round TKO

Adam Hamed def. Vojtech Hrdy via 1st round TKO

Denys Berincyk def. Anthony Yigit via unanimous decision (117-111, 115-113, 116-112)

Hamzah Sheeraz def. Dmytro Mytrofanov via second round TKO

Anauel Ngamissengue def. Fiodor Czerkaszyn by majority decision

Daniel Lapin def. Aro Schwartz via sixth round TKO