Berlin, Nov 16 (IANS): Heavyweight world champion Wladimir Klitschko knocked out unbeaten Kubrat Pulev in round five to defend his three boxing titles in Hamburg.

The Ukrainian defended his belts of the divisions IBF, WBO and WBA as he knocked out his Bulgarian contender in five to seal his 63rd win in his 66th fight Saturday night, reports Xinhua.

The 38-year-old has reigned supreme for eight years as heavyweight world champion. He suffered his last defeat 10 years ago when he lost to Lamon Brewster in Las Vegas, US.

Klitschko showed no mercy to Pulev as he dropped his opponent twice in the first round.

Klitschko kept going and sent the Bulgarian down for the third time in round three before he knocked him out in the fifth round with a left hook to the chin, with two minutes ans 11 seconds remaining.

With the victory Klitschko registered his 17th successful title defence while Pulev suffered his first loss in 21 fights.

"Pulev showed a good performance, he has my respect," Klitschko said after the fight.

"I feel great. I want a rematch as Wladimir had only luck this time," Pulev said.