Wladimir Klitschko has defended his WBO and IBF world heavyweight titles following a ninth round technical knockout victory over Ruslan Chagaev.

Chagaev was standing in for Britain's David Haye who had to pull out of the fight in Gelsenkirchen, Germany because of a back injury sustained in training.

Klitschko dominated the fight and had already sent Chagaev to the canvas before cutting him above the eye in the sixth round.

Although Chagaev bravely battled on, his corner decided to pull him out three rounds later.

Klitschko used his jab and superior movement to breakdown Chagaev's weak defence and easily picked off the Russian with combinations throughout the fight.

The Ukrainian rocked Chagaev in the first round with a straight right hand. The same punch then floored his opponent in the second round.

Having taken an eight-count Chagaev did well to make it through the rest of the second round.

But he was only delaying the inevitable as more punishment came his way. The Russian looked shaky in the fifth round as Klitschko landed a left-right combination.

The defining moment came when Klitschko cut Chagaev above the left eye with a powerful blow in the sixth round.

This gave Klitschko licence to attack even more and Chagaev's corner eventually decided their fighter should retire from the contest.

It was Chagaev's first defeat in 27 fights while Klitschko's record improves to 56 wins with 47 knockouts and three defeats.