Former heavyweight champion Ken Norton, who defeated Muhammad Ali in 1973, has died at the age of 70.

Norton passed away in a care facility in Arizona on Wednesday after suffering congestive heart failure, his close friend and former manager Patrick Tenore has confirmed.

Norton had been in poor health for several years and will be remembered for breaking Ali's jaw in their first of three fights, in which he went on to beat him in a split decision.

Ali narrowly won their second encounter by a split decision six months later before he claimed a second victory over Norton on September 28, 1976, at the Yankee Stadium in New York to retain his heavyweight title.

"It was early this (Wednesday) afternoon. Ken got congestive heart failure and passed away," Tenore said.

"He was recovering from a stroke which happened a year ago. To my shock his wife called me said he he had passed away.

"He was a fighter. He fought a tough battle and we thought he was out of the woods.

"He was a warm and generous man. He was a champion and a fighter and bright-eyed and anxious to see the next day and a dear friend of 20 years. Everyone will miss him. He never said a bad word about anyone."

Norton won the WBC heavyweight championship in 1977 when Leonard Spinks chose not to fight him, before he lost the title to Larry Holmes in a very close split decision in June the following year.

Norton finished with a record of 42-7-1 and 33 knockouts.

Following his boxing career, Norton made several film and television appearances before he suffered a near-fatal crash in 1986 when his car veered off the on-ramp to the Santa Monica Freeway in Los Angeles.

Despite being struck with ill health in later life, Tenore says Norton never blamed this on his professional boxing career, which began with a win over Grady Brazell in 1967 and ended with defeat against Gerry Cooney at Madison Square Garden in 1981.

"Ken Norton never blamed anyone for anything. He never had a bad word about boxing or any of his opponents. This is a man you have never heard say an ill word about anybody," Tenore added.

Reigning WBA super middleweight champion Andre Ward took to Twitter to express his condolences following Norton's death. He tweeted: "Just heard about Ken Norton passing. Met him last year in the Bay Area. Great champion & great man."

George Foreman, a former two-time heavyweight champion, said on Twitter: "They called us all handsome. Muhammad they called pretty. But The fairest of them all Ken Norton."

The World Boxing Council said: "The WBC regrets the passing away of our former champion Ken Norton. May he rest in peace".