British boxer Amir Khan with another superb picture of the great man. 

Khan also released a statement: "It is extremely sad to witness the passing of boxing's greatest fighter and icon Muhammad Ali. I would like to send my deepest condolences and thoughts to his family at this time. 

"No fighter or sportsman will ever reach the level of Muhammad Ali, whose name will continue to echo through the ages. Inspiring, charismatic, a true legend - Ali will never be forgotten. 

"Having the chance to meet the great man will be a memory and privilege I will always hold dear to me - an incredible human being, fighter and role model. Thank you Muhammad for inspiring us all."

The world of sport continues to pay its respects - here's an image from Sydney where the Australia and Greece football teams are locked at 0-0 with 68 minutes on the clock.

Image source, Getty Images

Boxing promoter Tommy Gilmour, who met Ali on a rare visit to Scotland, has paid tribute to the late fighter as "a champion in and out of the ring". 

Gilmour was just 12 when he was pictured with Ali during a trip to Glasgow in August 1965 for a bout against fellow American Jimmy Ellis. 

"I was one of the lucky ones to have met such a legend, it was more than 50 years ago but I can still remember it clearly. He had a presence. He was still a young man then but you did know that he was someone special. 

"I have been fortunate enough to have met many great fighters during my career but he was a very special man, and someone who stood up for his beliefs. If there was something he didn't believe in, he would fight it. He was a true champion both in and out of the ring." 

BBC Monitoring

Malaysian PM Najib Razak has tweeted: “The world lost more than just a legendary boxer. We lost the greatest of all time."

The numbers behind Muhammad Ali's career are staggering. He had 61 fights, of which he won 56 with 37 knockouts.

He boxed for 548 rounds in his professional career which began in 1960 and ended in 1981 and he went 31 fights before tasting defeat for the first time.

That was against Joe Frazier at Madison Square Garden in 1971. The pair met twice more over the next four years and Ali won both bouts.

Former world heavyweight champion Evander Holyfield pays his tribute.

BBC Radio 5 live commentator Conor McNamara never disappoints on Twitter...

Image source, Twitter

The marquee at Caesars Palace in Las Vegas - host to many top fights down the years - has paid this very public tribute to Muhammad Ali...

Image source, Getty Images

Mike Costello
BBC boxing correspondent

"I won't listen to an argument that he wasn't the best heavyweight of all time. There is no question he was the greatest and because of his influence outside the sport as well, he is unparalleled." 

Mike is taking part in a special programme on BBC Radio 5 live now and you can listen here.

Ben Dirs
BBC Sport

"In one five-minute interview, Ali could make you laugh more than Tiger Woods, Roger Federer, Lionel Messi and Tom Brady have in their entire careers combined. Actually, make that a five-second interview."

Read more from Ben here.

Ali, then Cassius Clay, fought British favourite Henry Cooper at Wembley Stadium in 1963, when he was knocked down by a left hook but recovered to win. Wembley have posted their own tribute today.

A look back at the life of boxing legend Muhammad Ali from 12:30 BST.

http://www.bbc.co.uk/programmes/b07dj3fz

Image source, Getty Images

BBC Radio 5 Live

There's a special Muhammad Ali programme on BBC Radio 5 live starting now. You can listen online here.

Ali visited Ireland in 1972 to fight Alvin Lewis at Croke Park, in a non-title fight the great man won by technical knockout in the 11th round. BBC Northern Ireland has put together a piece containing fascinating footage of the period, along with some tributes from leading Irish figures.

Watch the footage here

Or you can click on the link below in the BBC Newsline tweet.

BBC Monitoring

America is beginning to wake up to the sad news, and the New York Times eloquently captures the moment with a striking image on the front page of their website. And the words underline the enormity of his legacy.

Image source, New York Times

We've already spoken of Ali's fights with Henry Cooper, but it's fascinating to hear some of the stories behind the fights.

Ali would do training runs through Hyde Park with a dog named Cindy for company. He spent hours signing autograph and, 24 hours after the fight, walked around London in a pristine suit.

A low profile was not for him.

Muhammad Ali was aware of his legacy long before his death. After being asked how he would like to be remembered, he once said: "As a man who never sold out his people. But if that's too much, then just a good boxer. I won't even mind if you don't mention how pretty I was."

Let's be honest... it's hard not to realise how 'pretty' he was. He was that annoying bloke from school who was good at everything, was smart, witty, funny and pretty.

Here's a couple more classic Ali quotes, as promised earlier:

•  "I'll hit Liston with so many punches from so many angles he'll think he's surrounded."
• "You say I'm not the man I was 10 years ago. Well, I talked to your wife and she says you're not the man you were 10 years ago!" Ali to legendary boxing commentator Howard Cosell.