Gennady Golovkin has retained his IBF and WBC middleweight titles after defeating Kell Brook in the fifth round at the O2 Arena in London.

The contest was brought to a close when Brook's trainer Dominic Ingle threw in the towel with the Briton hanging onto the ropes, taking brutal body blows.

IBF welterweight champion Brook stepped up two weights to take on the man widely regarded as the best pound-for-pound fighter on the planet. But despite a gutsy performance that will only serve to enhance his reputation, he was unable to halt the Kazakh's reign of dominance.

Speaking post-fight, Brook said his eye-socket had been been broken by Golovkin during their battle. "I think he was catching me with my biggest shots. I was able to get through them," the 30-year-old said.

"Believe me, I hurt him, When you're in a fight, you can see every movement of a fighter. I take nothing away from him, I would fight him again. I think the fans enjoyed it. When you see five of them, you don't know which one to hit."

34-year-old Golovkin was the overwhelming favourite ahead of the fight but Brook engaged him in a gripping exchange in the opening round, despite being rocked by an early body blow. The Briton stood his ground in the second and third, landing his share of jabs that bounced off the Kazakh, but Golovkin's huge body hooks began inflicting more and more damage as the contest wore on. By the fifth round, the reigning champion had stalked the challenger into the corner before unleashing another thunderrous flurry, prompting Ingle to throw the towel in.

Speaking post-fight, Golovkin issued a challenge to WBO middleweight champion Billy Joe Saunders, also insisting he is still open to fighting Saul 'Canelo Alvarez. Brook meanwhile would appear to have no plans to return to welterweight, telling the crowd after the fight he would like to fight the winner of Canelo vs Liam Smith, who fight in Texas next week with the Mexican's WBO super-welterweight title on the line.