Steve Irwin, the Australian crocodile hunter and television naturalist, died earlier today on a diving trip after being stung through the heart by the poisoned tail barb of a stingray. He was 44.

John Howard, the Australian Prime Minister, who picked Irwin to attend a barbecue in honour of President Bush's visit to Australia in 2003, said he was "shocked and distressed at Steve Irwin's sudden, untimely and freakish" death.

"It's a huge loss to Australia," Mr Howard said. "He was a wonderful character. He was a passionate environmentalist. He brought joy and entertainment and excitement to millions of people."

Irwin rose to fame in the 1990s by riding the popularity of Paul Hogan's Crocodile Dundee movies, but his real-life exploits on the Discovery cable television channel and his larger-than-life personality ended up making him more famous than his fictional forebear.

His amazed shout of "Crikey!" when faced with a huge crocodile, poisonous snake or menacing-looking spider - which he would invariably then go on to manhandle - helped to transform him into an Australian icon around the world.

Hollywood paid the ebullient, blond-haired Aussie the ultimate accolade when he was invited to play himself in a cameo role in the Eddie Murphy animal caper Dr Doolittle 2.

Although he was criticised for being irresponsible two years ago when he dandled his one-month-old baby son, Bob, while feeding a 13ft crocodile at his Australian Zoo reptile park in the north-eastern state of Queensland, no official action was taken over the incident.

Chastened, Irwin retreated from public life for a few weeks, but in the end the incident probably merely added to the mythology built up around him of the quintessential Australian larrikin.

Bernard Lagan, Times correspondent in Sydney, said that it was Irwin's personality that his fellow countrymen were going to miss. "He was the real Crocodile Dundee, probably more famous now than Hogan - the archetypal big, loud, bear-like Aussie, full of bonhomie and one-liners," said Lagan.

"Children in particular loved him. He seemed to really care about all kinds of animals, and often made little films for kids about how to look after their dogs and cats, as well as his daredevil exploits with crocs and sharks.

"His efforts on conservation were taken seriously, he went into bat against development in environmentally sensitive areas, and against the mass culling of wild animals. In terms of cold, hard cash, he will be a big loss to the Australian tourism industry. He was really, really big in the US, where his Crocodile Hunter show ran up to seven times a day on cable television. His zoo in Queensland employs around 500 people."

Irwin was snorkelling in shallow waters off the Great Barrier Reef, off Queensland, as his cameraman filmed a sequence on large male stingrays for his daughter's new TV series, Ocean's Deadliest, when he swam too close to one of the rays at 11am (0200 BST) this morning.

Stingrays are normally peaceable creatures, nicknamed the "pussycats" of the seas and sometimes content to allow scuba divers to hitch a ride on their backs, but when startled - usually by being trodden on - they are capable of delivering a dose of toxic venom with the sharp, barbed stinger which is situated like a bayonet at the end of their whiplash tails.

"He came on top of the stingray and the stingray's barb went up and into his chest and put a hole into his heart," said John Stainton, his producer and closest friend, who was on board Irwin's boat at the time.

Deaths from such attacks are very rare - it is believed that previously there have been only two recorded incidents in Australian waters, and the last was more than 50 years ago - but Irwin appears to have been exceptionally unlucky in being struck in the heart.

His film crew got him to his rescue vessel, Croc One, and set off at top speed to Low Isle on the Barrier Reef to rendezvous with doctors. They kept trying to resuscitate him, but by the time medics arrived in the Queensland medical helicopter at noon he was past help.

Dr Ed O'Loughlin, who attended, said: "It became clear fairly soon he had non-survivable injuries. He had a penetrating injury to the left side of his chest, he had lost his pulse and wasn't breathing."

The Queensland Police Service confirmed his death after managing to contact Irwin's wife Terri, originally from the American state of Oregon, who was hiking in a remote, mountainous part of Tasmania when the accident happened. She has broken the news to the couple's two children - Bhindi Sue, eight, and Bob, two.

Irwin's body has been taken to a morgue in Cairns, where friends and family are gathering.

Mr Stainton gave an emotional statement from aboard Croc One, saying: "The world has lost a great wildlife icon, a passionate conservationist and one of the proudest Dads on the planet. He died doing what he loved best. He left this world in a peaceful state of mind. He would have said: 'Crocs rule!'"

Tributes poured in, although some of those who spoke struck a sceptical note. Ray Mears, a television survival expert, said the Australian’s death was a tragedy but added that it proved "some things in nature should be left alone".

Mr Mears said: "He clearly took a lot of risks and television encouraged him to do that. It’s a shame that television audiences need that to be attracted to wildlife.

"Dangerous animals, you leave them alone because they will defend themselves. Nature defends itself, it isn’t all about hugging animals and going ‘ahh’. It’s wonderful to observe but you have to be sensible and maintain a safe distance."

He continued: "Television has become very gladiatorial and it’s not healthy. The (wildlife) voyeurism we are seeing on television has a cost and it’s that cost Steve Irwin’s family are paying today."

But Dr David Bellamy, the conservationist, said: "He was magic and for the world of conservation and natural history to lose him is very, very sad. The thing with Steve was he mixed damn good science with showbusiness and I don’t know anyone else who did that.

"I’m quite sure all the crocs in Australia are smiling, not crocodile tears, because he made them famous. When I heard this morning I cried, the world really has lost a very, very important natural historian."

Mark O’Shea, a British zoologist, said that although some "university professors" might have turned their noses up at the way presenters like Irwin portrayed reptiles, he had probably inspired many people to follow a future in conservation.

"A lot of people who now want to study biology and work with animals may not have considered it before they watched him on television," he said.

At Australia Zoo at Beerwah, south Queensland, floral tributes were dropped at the entrance, where a huge fake crocodile gapes. Drivers honked their horns as they passed.

"Steve, from all God's creatures, thank you. Rest in peace," was written on the card with one bouquet.

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