MOSCOW - Ukraine's Vitali Klitschko successfully defended his WBC heavyweight title on Saturday night after the referee stopped his bout with Germany's Manuel Charr in the fourth round due to a cut over the challenger's right eye.

The fight was stopped with 56 secinds remaining in the round.

Klitschko improved his record to 45-2, while Charr, who was unbeaten before his meeting with Ukraine's 41-year-old veteran, fell to 21-1.

"I was a bit disappointed as I wanted to win today by a real knockout, not a technical one," said Klitschko.

"I was ready to continue the bout and Charr was also ready for further boxing but it was the decision of the doctor and the referee, who are responsible for it and we could do nothing about it.

Fighting in the 30,000-seater Olimpiyski indoor sports arena, the hugely-experienced Klitschko started the bout as a hot favourite in what was his 17th world heavyweight championship fight.

Charr, 27-years-old, brought with him an unblemished record in 21 fights and a seventh ranking by the WBC, but none of his opponents had been of the highest calibre.

The much smaller Charr was immediately on the defensive as the towering Klitschko stalked him behind his powerful jab and it was only in the closing seconds that the German attempted a couple of tentative punches.

Klitschko stayed well on top in the second round and he sent Charr crashing to the floor seconds before the bell for a standing eight count with a right hook to the side of the head.

The German challenger recovered well though and caught Klitschko with a brief flurry of punches in the third, but it was the Ukrainian who again won the round.

The fight then came to an abrupt end in the fourth when a Klitschko left hook brought a gush of blood from above Charr's right eye and the referee was quick to step in and end the contest.

The German was furious with the decision, kicking the ropes in his anger, but it was clear from the amount of blood that there was no way he could continue.

"In the first two rounds Charr was concentrated on defence only and it was slightly difficult for me as I like it better when my opponents are fighting back," Klitschko said.

"In the third and fourth he started to come out of his shell more and I had more chances to attack.

"But Charr is a true fighter. He was ready to fight to the end. I think this defeat will not stop him and I believe he has chances for a promising career in boxing."