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 was 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, including seven majors.
Arnold Palmer was the most important golfer to play the game, says BBC's golf correspondent Iain Carter.
His force of charisma put the game on the map and it never dimmed, he adds.
Palmer attracted thousands of diehard fans known as "Arnie's Army" and helped to promote the game into the television age.
"Today marks the passing of an era," said Alastair Johnston, CEO of Arnold Palmer Enterprises.
"Arnold Palmer's influence, profile and achievements spread far beyond the game of golf. He was an iconic American who treated people with respect and warmth, and built a unique legacy through his ability to engage with fans."
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 who later became the professional at the golf club there.
Palmer 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.