LAS VEGAS -- An ugly heavyweight fight turned really ugly when Kirk Johnson kept hitting low. It ended when he punched WBA champion John Ruiz below the belt for at least the fourth -- and final -- time.

	Referee Joe Cortez takes a point from Kirk Johnson after his low blow on John Ruiz in the first round.

Ruiz, floored in three earlier rounds by low blows, was declared the winner in his title defense against Johnson on Saturday night when the challenger threw yet another punch below the belt in the 10th round.

Referee Joe Cortez, who had already penalized Johnson one point on two occasions, halted it by disqualifying Johnson at 2:17 of the 10th.

A 2-1 underdog, Ruiz was winning the fight on all the judges' cards -- by two scores of 85-84 and another of 86-83 -- despite having to take time out the three earlier times he was hit low.

He also had the previously unbeaten Johnson in trouble late in the ninth round, catching him with a hard right that caused Johnson to clutch him. Ruiz wrestled him down, and Johnson sort of tackled Ruiz as he went to the canvas and both went sprawling.

The round ended shortly afterward.

"I caught him with a good right and I was trying to let loose and I pushed him off me and he just fell down,'' Ruiz said.

A round earlier, Ruiz had to wait five minutes to resume after Johnson hit him low.

"I don't know what he was thinking,'' Ruiz said. "I came out fighting clean, and he hit me low and I had to catch my breath. It took me out of my game plan.''

Johnson admitted he lost focus.

"I was starting to feel good, but then I don't know what happened,'' he said. "It was terrible, man. It was my fault.''

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 to a knee, then, after resting briefly, motioned to Cortez that he was ready to resume.

Ruiz then charged Johnson, with the two reeling into the ropes, where Ruiz head-butted the challenger. Cortez separated and warned them both.

"I was just ticked off,'' Ruiz said. "He just kept hitting me down low. There is only so much I can take. I had to restrain myself.''

Ruiz also went down from a low blow in the first, with Cortez giving him a few moments to recover and penalizing Johnson for the hard left hook below the champion's belt.

"I had a lot of emotion,'' Johnson said. "I wanted to be impressive and sometimes when you want to impress, you don't. I wanted to fight impressively so I could fight Lennox Lewis next.

"Some of the punches were borderline. He crouched down and I tried to hit him in the middle coming up, but a couple of times I strayed low.''

Johnson was warned but not penalized for the low blow in the fourth round of the fight that drew a crowd of 6,572 to the Mandalay Bay Events Center arena configured for 8,500 seats.

Ruiz, from Chelsea, Mass., improved to 38-4-1, with 27 knockouts. Johnson, from North Preston, Nova Scotia, dropped to 32-1-1.

Ruiz earned $1.5 million for the fight, and Johnson got $1 million.

Lewis, who unified the WBC, IBF and WBA titles by beating Holyfield in 1999, surrendered the WBA crown later that year, opting to fight Michael Grant rather than make a mandatory defense against Ruiz.

Ruiz and Evander Holyfield then met three times with the WBA crown at stake. Holyfield won the first bout on a disputed decision in August of 2000, Ruiz came back to take a clear-cut decision and win the title in March of 2001, then retained it when they fought to a draw last December.

Those three rugged matches proved a redemption of sort for Ruiz, whose career had been noted for a fight against David Tua in 1996, when Tua knocked him out 19 seconds in. Tua was ringside for the fight against Johnson.

The only blemish on Johnson's record was a draw against Alfred Cole on Dec. 8, 1998, but the Canadian won six straight after that, including a 10-round decision over Cole in their March 20, 1999, rematch.