Image caption Ken Norton and Muhammad Ali during their second meeting in 1973

Former US heavyweight boxing champion Ken Norton, who beat Muhammad Ali, has died at the age of 70, his son says.

Norton, who had been in poor health following a series of strokes, died at a care facility in Las Vegas, Nevada.

He broke Ali's jaw in their first bout in San Diego, California, in 1973, which Norton won.

In their last meeting on September 1976 at New York's Yankee Stadium, Ali won a narrow and controversial decision to retain the heavyweight title.

"I'm sure he's in heaven now with all the great fighters," Gene Kilroy, Ali's former business manager, told the Associated Press news agency. "I'd like to hear that conversation."

Norton began boxing during his time in the US Marines, and turned professional shortly after he left the military in 1967.

He was named heavyweight champion in 1978 after defending champion Leon Spinks refused to fight him, but lost three months later in a classic 15-round fight with Larry Holmes.

After his boxing career ended, Norton appeared in several movies and became a fight commentator.

He had five children, one of whom went on to play professional football and now coaches in the National Football League for the Seattle Seahawks.