AP Photo/FILE
Heavyweight boxer Muhammad Ali makes a point during a news conference that he conducts from inside the ring in Atlanta, Ga., in this Oct. 24, 1970, file photo
Ali had been suffering from respiratory issues this week, apparently related to his Parkinson's disease, and was hospitalized in Arizona.
AP Photo/Fabian Bimmer
Former heavyweight boxing legend Muhammad Ali waves to the audience after receiving the "Bambi Trophy" during the Bambi Media Award in Hamburg, northern Germany, Thursday evening, Nov. 27, 2003.
Ali, 74, was diagnosed with Parkinson's in the 1980s, but remained active for much of the past 30 years, despite challenges caused by the neurological disease.
News of Ali's rapidly deteriorating health Friday marked a significant downturn for the former boxer whose condition was described by doctors as "fair" the day before.
AP Photo/Mark Lennihan, FIle
Muhammad Ali.
Ali had been hospitalized several times over the years, most recently in early 2015.
The Hollywood Reporter noted that he looked "increasingly frail" in public appearances, "including April 9 when he wore sunglasses and was hunched over" during an event in Phoenix.
Ali's daughter, Laila, who was an undefeated boxer herself, was reportedly among Ali's nine children with him at the hospital in Arizona.
She thanked fans for their support and posted a baby picture of her daughter, Sydney, who was born in 2011, being held by the boxing legend.
"It's a sad day for life, man. I loved Muhammad Ali, he was my friend. Ali will never die," Don King, who promoted some of Ali's biggest fights, told The Associated Press early Saturday.
"Like Martin Luther King, his spirit will live on, he stood for the world," he said.
Despite the debilitating effects Parkinson's disease had on Ali's body, it never seemed to daunt the boxing legend's spirit. Ali remained a charismatic presence in public.
Born Cassius Marcellus Clay on January 17, 1942 in Louisville, Kentucky, Ali started boxing at age 12. It was an early start to what would eventually become a storied career.
A towering figure in his prime, he still traveled and made appearances in his later years despite being muted by the thousands of punches he took during his remarkable career.
AP Photo/John Rooney
Heavyweight champion Muhammad Ali stands over fallen challenger Sonny Liston, shouting and gesturing shortly after dropping Liston with a short hard right to the jaw on May 25, 1965, in Lewiston, Maine.
He beat the invincible Sonny Liston, fought a string of thrilling fights with Joe Frazier and stopped George Foreman in the "Rumble in the Jungle" in Zaire. But he paid a terrible price for the estimated 29,000 punches he took to his head during a career that made him perhaps the most recognized person in the world.
Ali never complained about the price he paid in the ring.
"What I suffered physically was worth what I've accomplished in life," he said in 1984. "A man who is not courageous enough to take risks will never accomplish anything in life."
The Associated Press contributed to this report