In a statement released on Twitter, Nicklaus said Palmer was one of his best and closest friends and he “will miss him greatly.”

The full statement from the 18-time major winner read:

"I just got the news at about 8:45 that Arnold had passed. I was shocked to hear that we lost a great friend—and that golf lost a great friend.

At this point I don’t know what happened, and I suppose it is not important what happened. What is important is that we just lost one of the incredible people in the game of golf and in all of sports. My friend—many people’s friend—just wore out. I know he was in Pittsburgh trying to find out how to make himself better. That’s what Arnold has always tried to do. He has always been a fighter and he never gave up on anything. He didn’t give up even now. Maybe his body did, but I know Arnold’s will and spirit did not.

Jack Nicklaus and Arnold Palmer at the height of their on-course rivalry. PHOTO: Getty Images.

I wish I had another chance to talk to him, but I am so glad we talked a couple weeks ago on his birthday (Sept. 10), when he sounded great. So Barbara and I are just in shock and incredibly saddened. Our hearts, thoughts, prayers and sympathies go out to Kit, his kids, grandkids, great grandkids, and his entire loving family.

He was one of my best friends, closest friends, and he was for a long, long time. I will miss him greatly.

Arnold transcended the game of golf. He was more than a golfer or even great golfer. He was an icon. He was a legend. Arnold was someone who was a pioneer in his sport. He took the game from one level to a higher level, virtually by himself. Along the way, he had millions of adoring fans—Barbara and I among them. We were great competitors, who loved competing against each other, but we were always great friends along the way. Arnold always had my back, and I had his. We were always there for each other. That never changed.

He was the king of our sport and always will be."

Five-time Open Champion Peter Thomson called Palmer “the folk hero of golf.”

“Not only was he the greatest personality the game has produced, he was King of the fairways every time he played,” Thomson said in a statement issued by Golf Australia.

“We were only two weeks apart in age and great rivals. We certainly had some wonderful times together.

“The last time we played was an exhibition at The Australian Golf Club in Sydney on November 24, 2004. The occasion was the centenary of the Australian Open and Bruce Devlin joined us for the nine-hole match on the eve of the tournament.

Peter Thomson, Palmer and Bruce Devlin at The Australian GC in 2004. PHOTO: Getty Images.

At last year's Open Championship at St Andrews, we were rival captains in the four-hole Past Champions event and, although our team scores were the same, Arnold's team won the charity donation by being the older team of the two.

“St Andrews was a fitting final place for us both to meet.

Mary and I are terribly saddened by the news of his death, and our thoughts are very much with Kit, and his daughters and their families.

“Bless you always, Arnold.”

Former World No.1 Tiger Woods also released a statement.

"It's hard to believe that Arnold has passed, and I'm deeply saddened by his loss. He meant so much to the game and to me personally. I knew that I could always call him for advice, and I looked forward to seeing him at Bay Hill and the Masters,” Wood said.

Arnold touched so many people. My kids were born at the Winnie Palmer Hospital for Women & Babies, and his philanthropic work will be remembered along with his accomplishments in golf. It was an honour and privilege to have known Arnold, and I'm forever grateful for his friendship."

Tiger Woods and Palmer share a joke during the presentation ceremony at Bay Hill. PHOTO: Getty Images.

A who’s who of the golfing world and beyond also took to social media to pay their respect to the ‘King’.

“Here’s to The King who was as extraordinary on the links as he was generous to others. Thanks for the memories, Arnold.” – President Barack Obama.

“Arnie put the game on the map. Don't think any other sportsperson in any sport did for their profession what Arnie did for the game.” – Rory McIlroy.

“I’ll miss you friend.” – Rickie Fowler.

“Just heard the news about #TheKing. Can't believe it. Amazing man and his legacy in the game and in our hearts will live forever.#RIPArnie.” – Graeme McDowell.

“We loved him with a mythic American joy. He represented everything that is great about golf. The friendship, the fellowship, the laughter, the impossibility of golf, the sudden rapture moment that brings you back, a moment that you never forget, that’s Arnold Palmer in spades. He’s the defining figure in golf.” – James Dodson, Arnold Palmer’s biographer.

“I’m one of the fortunate folks to have spent time with the King. Incredibly blessed to have known him.” – David Duval.

“RIP #arnoldpalmer. You changed the game with your charisma and personality. Every player, me included, should thank you for what you brought to our great game. You had this incredible ability to open the eyes of the world to the beauty of golf. You played with Presidents, celebrities and CEO’s. In doing so you opened the game to commercialisation. For that I thank you. Our sport will always remember you. I will miss you.” – Greg Norman.

“So sad to hear Mr Palmer has passed away. He touched us all and was an incredible role model. The KING.” – Jason Day.