American John Ruiz retained his WBA heavyweight title in Las Vegas on Saturday after his opponent Kirk Johnson was disqualified.

It was Ruiz's second successful defence of the title he won from Evander Holyfield last year.

The Canadian, who was previously unbeaten, was stopped in the 10th round for repeated low blows.

The fight was stoppped at two minutes and 17 seconds into the round by referee Joe Cortez after Johnson's third low blow.

Below the belt

Ruiz was winning the fight on all the judges' cards despite having to take time to recover from the earlier low blows by Johnson.

The bout turned nasty in the fourth, when Johnson - for the second time in the fight - hit Ruiz below the belt with a hard left hook.

Ruiz went down on his knee, then, after resting briefly, indicated to the referee that he was ready to resume.

Ruiz then charged Johnson, sending both fighters into the ropes, where they appeared to exchange head butts. Cortez separated and warned them both.

Then in the eighth round Ruiz had to wait five minutes to resume after another Johnson low blow.

He recovered and had Johnson reeling late in the ninth round.

It was Ruiz's 38th win in 43 fights.