Ali family gathers at boxing legend's hospital bedside
The family of boxing great Muhammad Ali has gathered at his hospital bedside in Arizona, as the 74-year-old former heavyweight champion battles respiratory problems.
Ali's respiratory issues have been complicated by the Parkinson's that he was diagnosed with in the 1980s, sources have said.
The sources, who did not want to be identified because they were not speaking on behalf of the family, described Ali's condition as being very concerning to family members.
Several of Ali's daughters reportedly flew to Phoenix late on Thursday and early Friday to be with their father.
A spokesman for Ali said there was no update on his condition and Ali's long-time Parkinson's specialist Dr Abraham Lieberman, of the Barrow Neurological Institute in Phoenix, declined to comment.
"I can't really say much more than what's in the papers," he said.
Ali has been admitted to hospital several times in recent years, most recently in early 2015 when he was treated for a severe urinary tract infection initially diagnosed as pneumonia.
He has looked increasingly frail in public appearances, including on April 9 when he wore sunglasses and was hunched over at the annual Celebrity Fight Night dinner in Phoenix, which raises funds for Parkinson's treatment .
His last formal public appearance before that was in October when he appeared at the Sports Illustrated Tribute to Muhammad Ali at The Muhammad Ali Centre in his home town of Louisville, Kentucky, along with former opponents George Foreman and Larry Holmes.
Ali has suffered from Parkinson's for three decades, most famously trembling badly while lighting the Olympic torch in 1996 in Atlanta. Despite the disease he kept up a busy appearance schedule until recently, though he has not spoken in public for years.
Doctors say the Parkinson's was probably caused by the thousands of punches Ali took during a career in which he travelled the world for big fights.
An iconic figure who at one point was perhaps the most recognised person in the world, Ali has lived quietly in the Phoenix area with his fourth wife Lonnie, whom he married in 1986.
News of his hospital admission brought well wishes from boxers and others on Twitter, including Sugar Ray Leonard, who modelled his career after Ali's.
"Prayers & blessings to my idol, my friend, & without question, the Greatest of All Time @MuhammadAli ! #GOAT," Leonard wrote.
Laila Ali, herself a former boxing champion, posted a picture on Facebook of her father holding her daughter when she was an infant.
"I love this photo of my father and my daughter Sydney when she was a baby!" she wrote. "Thanks for all the love and well wishes. I feel your love and appreciate it!!"