Boxing legend Muhammad Ali is reported to be in grave condition

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Heavyweight champion Muhammad Ali stands over fallen challenger Sonny Liston, shouting after knocking him down with a short, hard right to the jaw during their bout in Lewiston, Maine, on May 25, 1965. (John Rooney / Associated Press)

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Muhammad Ali listens to a Nation of Islam speech at Chicago’s Coliseum in 1968. ( Jim O’Leary / Chicago Tribune)

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A Zairian in traditional clothing leads Muhammad Ali through a crowd at the airport in Kinshasa, Zaire (now known as Congo). Ali arrived in a chartered Air Zaire plane from Paris for a 1974 world championship fight with George Foreman, the famed “Rumble in the Jungle.”

(Horst Faas / AP)

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Muhammad Ali stands in the ring at the Windy City Boxing Club with gym owner Clarence Griffin in 1977.

(Luigi Mendicino / Chicago Tribune )

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Muhammad Ali speaks during an interview in 1977 for a French television program in Paris. (Patrick Riviere / Getty Images)

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Muhammad Ali attends Chicago’s Independence Day Parade in 1979.

(Michael Budrys / Chicago Tribune)

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Muhammad Ali watches as the flame climbs up to the Olympic torch while taking part in the opening ceremonies of the 1996 Atlanta Olympic Games. (Doug Mills / Associated Press)

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Muhammad Ali signs a poster-size replica after being honored with the 2,189th star on the Hollywood Walk of Fame, during an unveiling ceremony in 2002 in Los Angeles.

(Jim Ruymen / Reuters)

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Joe Frazier sits with Muhammad Ali at the NBA All-Star Game in 2004 in Philadelphia.

(George Reynolds / McClatchy-Tribune)

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Golfing legend Arnold Palmer shakes hands with three-time world heavyweight boxing champion Muhammad Ali as basketball player Dwyane Wade looks on Jan. 2, 2007, before the Orange Bowl between Louisville and Wake Forest. (Lynne Sladky, AFP/Getty Images)

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Muhammad Ali attends a game between the Phoenix Suns and the San Antonio Spurs on March 9, 2008, at US Airways Center in Phoenix.

(Lisa Blumenfeld / Getty Images)

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Muhammad Ali attends the Norman Mailer Center’s fourth annual Benefit Gala on Oct. 4, 2012, in New York City.

(Stephen Lovekin / Getty Images)

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The “I Am The Greatest, Muhammad Ali” exhibition at the O2 arena, which hosts high profile boxing fights in London, on June 4, 2016.

(Matt Dunham / AP)

By Lance Pugmire

June 3, 2016 3:13 PM PT

Muhammad Ali’s family is at his bedside in a Phoenix hospital and two sources close to the legendary former heavyweight champion told the Los Angeles Times that the situation is “very grave.”

Ali, who’s suffered from Parkinson’s disease for more than 20 years, was hospitalized Thursday with a respiratory illness. He reportedly was placed on life support Friday.

The boxing officials close to Ali and in contact with his family spoke on condition of anonymity out of respect to the three-time heavyweight champion and sports icon.

One of the officials said Ali’s condition has deteriorated to the point that an individual close to the situation has said “it could be hours” before his passing.

In this Sept. 27, 2014, file photo, Muhammad Ali is shown before the Ali Humanitarian Awards ceremony in Louisville, Ky. A spokesman for boxing great says Ali is being treated in a hospital for a respiratory issue.

Ali’s longtime Parkinson’s doctor declined comment when reached by the Associated Press Thursday night.

“I can’t really say much more than what’s in the papers,” said Dr. Abraham Lieberman of the Barrow Neurological Institute in Phoenix.

Several of Ali’s daughters reportedly flew to Phoenix late Thursday and early Friday to be with their father.

Laila Ali, herself a former boxing champion, posted a picture Friday afternoon 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!!”

Ali has been hospitalized several times in recent years, most recently in early 2015 when he was treated for a severe urinary tract infection initially diagnosed as pneumonia.

Ali has looked increasingly frail in public appearances, including April 9 when he wore sunglasses and was hunched over at the annual Celebrity Fight Night dinner in Phoenix, which raises funds for treatment of Parkinson’s.

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 Center in his hometown 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 likely was caused by the thousands of punches Ali took during a career in which he traveled the world for big fights.

An iconic figure who at one point was perhaps the most recognized 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 hospitalization brought well wishes from boxers and others on Twitter, including Sugar Ray Leonard, who modeled his career after Ali’s.

“Prayers & blessings to my idol, my friend, & without question, the Greatest of All Time @MuhammadAli ! #GOAT,” Leonard wrote.

The Associated Press contributed to this report