US golfer Arnold Palmer, viewed as one of the greatest players in the sport's history, has died at the age of 87.
Palmer died at the UPMC Presbyterian Hospital in Pittsburgh, Pennsylvania, where he had been undergoing heart tests, the Pittsburgh Post-Gazette reported.
The United States Golf Association also confirmed his death in a tweet calling him "golf's greatest ambassador".
During a long career, he won more than 90 tournaments worldwide.
Palmer attracted thousands of diehard fans known as "Arnie's Army" and helped to promote the game into the television age.
Golfer Tiger Woods tweeted: "Thanks Arnold for your friendship, counsel and a lot of laughs. Your philanthropy and humility are part of your legend."
Arnold Palmer was born in Latrobe, Pennsylvania, in 1929, the son of a groundskeeper at the local country club.
He was one of golf's most dominant players in the late 1950s and early 1960s, winning seven major titles over seven seasons.
He also notched up 62 PGA Tour wins.