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

The boxing legend, formerly known as Cassius Clay, died on June 3 at a hospital in Phoenix, Arizona. He was 74.

Muhammad Ali 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 June 9 in his hometown of Louisville in Kentucky.

Boxing legend Muhammad Ali has been taken to hospital after falling unconscious at home just days after his frail appearance at a funeral for Joe Frazier

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

Former 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 June 4, 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.

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

Soon after retiring, rumors began to circulate about the state of Muhammad Ali’s health. His speech had become slurred, he shuffled and he was often drowsy.

Parkinson’s syndrome was eventually diagnosed but Muhammad Ali continued to make public appearances, receiving warm welcomes wherever he traveled.