Boxing legend Muhammad Ali died of “septic shock due to unspecified natural causes”, his family has said.

The three-time world heavyweight champion – one of the world’s greatest sporting figures – died on Friday night at a hospital in Phoenix, Arizona.

The 74-year-old had been suffering from a respiratory illness, a condition that was complicated by Parkinson’s disease.

A public funeral will be held for the boxer on Friday in his hometown of Louisville in Kentucky.

“He was a citizen of the world and would want people from all walks of life to be able to attend his funeral,” said the family spokesman, Bob Gunnell.

Former US President Bill Clinton is among those who will give a eulogy at the service, and was one of many prominent global figures who paid tribute to Ali on Saturday, saying he lived a life “full of religious and political convictions that led him to make tough choices and live with the consequences”.

The legendary Brazilian footballer, Pele, said the sporting universe had suffered a huge loss.

“Muhammad Ali shook up the world. And the world is better for it,” said US President Barack Obama.

Ali was as much a campaigner for black equality as he was a champion in the ring, where he won 56 of his 61 fights.

Asked how he would like to be remembered, he once said: “As a man who never sold out his people. But if that’s too much, then just a good boxer. I won’t even mind if you don’t mention how pretty I was.”

•Excerpted from a BBC report. Photo shows late Muhammad Ali.