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Ukrainian heavyweight titleholder Vitali Klitschko celebrates after defeating Cuban challenger Odlanier Solis during their WBC heavyweight world championship boxing match in Cologne, Germany on Saturday. ((Patrik Stollarz/AFP/Getty Images))

Vitali Klitschko retained his WBC heavyweight title with a late first-round knockout of Odlanier Solis, who injured his knee in the fall and insisted it was that — and not the champion's punch — that ended the fight Saturday.

Klitschko's right to Solis' left temple staggered the Cuban, who wobbled back then fell on his back and clutched his right knee.

Solis managed to beat the count but was unsteady on his feet as referee Jose Guadalupe Garcia of Mexico called the fight.

"It was a full blow," Klitschko said in the ring, with the crowd in Cologne's indoor arena booing.

Klitschko's punch came in the final second of the first round, after Solis hit him on the chin with a right.

"It was definitely my knee," Solis said, also in the ring. "It could be that I took a wrong step."

He hobbled with help back to his dressing room and was taken to a hospital on a stretcher to have a scan on his knee.

Solis' promoter Ahmet Oner insisted it was the injury and not Klitschko's blow that ended the fight.

"He will now have a scan and probably have surgery immediately. He seems to have torn ligaments," Oner said.

The sudden end stunned the crowd, which booed and whistled for a long time.

Solis, a 30-year-old former three-time world amateur champ, fell to his first defeat in 18 pro fights.

The 39-year-old Klitschko improved to 42-2.

Solis fought a solid first round, taking the initiative and connecting with a couple of rights despite giving up six inches in height to the Ukrainian, who relied on his left jab until the last-second punch.

Vitali's younger brother Wladimir, the IBF and WBO champ, fights WBA belt-holder David Haye in June or July.

Solis, the 2004 Olympic champ, beat Haye to win one of his amateur world titles.