There were only five seconds left in the 12th round when the Ukrainian sent Chambers to the floor with a left hook.

It was the 33-year-old champion's 48th knockout win in 57 contests and he dominated the fight behind a solid jab against a defensively-minded opponent.

"I don't think he ever really hit me, but it wasn't easy. I wanted to be too perfect maybe," said Klitschko.

"I do not feel my age at all. I just feel that I keep getting better and better. There is more where this came from."

The American challenger, known as 'Fast Eddie', had only lost once in 36 previous contests but was conceding five inches in height and 35lbs in weight.

After an unremarkable opening round, the second saw Chambers, 27, duck and hoist Klitschko on his shoulder before dumping him on the canvas.

The champion responded with a big right later in the round but was unable to finish the job and the pattern was set for a largely dull encounter with Klitschko, who was in the ring for the first time in 10 months, using his left jab as his main weapon.

Chambers did land a good right in the fifth but it had little effect on the champion and he was content to try and limit the damage, much to the annoyance of his corner.

There was a break at the end of the ninth to allow Chambers to change a split right glove but the breather seemed to benefit Klitschko more.

He pursued Chambers round the ring in the final round looking to land a knockout punch and finally succeeded with a looping left, the referee not even bothering with the formality of a count.

Klitschko would now like to meet Britain's David Haye, the WBA champion, having said before taking on Chambers: "I would prefer to fight him in a soccer arena but I would also face him in a car park if necessary."

But he acknowledged afterwards that a showdown with Haye, who makes the first defence of his title against American John Ruiz in Manchester on 3 April, may have to wait for a while.

"We will see who my next opponent will be, but I believe Alexander Povetkin is my official IBF challenger and we can quickly start discussions for that fight," Klitschko added.

BBC