''He came over the top of a stingray and the stingray's barb went up and went into his chest and put a hole into his heart,'' Irwin's shocked manager John Stainton told reporters in Cairns, south of Port Douglas.

A helicopter rushed paramedics to nearby Low Isles where Irwin was taken for treatment, but he was dead before they arrived, emergency officials said.

''It became clear fairly soon that he had non-survivable injuries,'' Dr. Ed O'Loughlin, who treated Irwin, told Nine Network television.

''He had a penetrating injury to the left front of his chest. He had lost his pulse and wasn't breathing,'' he said.Irwin's death was likely only the third recorded fatal stingray attack in Australia, experts said. They said stingray venom was agonizingly painful but not lethal, although the barb was capable of causing horrific injuries like a knife or bayonet.

''It's not the going in, it's the coming out,'' Australian Venom Research Unit deputy director Bryan Fry told Reuters. "They have these deep serrations which tear and render the flesh as it comes out,'' he said

Known around the world for his catchphrase "Crikey'' during close encounters with wild animals, Irwin made almost 50 documentaries which appeared on the cable TV channel Animal Planet. 

"I really do feel Australia has lost a wonderful and colourful son. He brought immense joy to millions of people, particularly to children, and it's just such a terrible loss,'' emotional Australian Prime Minister John Howard told reporters.

British naturalist and broadcaster David Bellamy described Irwin as a great performer and an excellent natural historian. Born on February 22, 1962, in the southern Australian city of Melbourne, Irwin moved to tropical Queensland where his parents ran a small reptile and fauna park.

He met his U.S.-born wife Terri at the Australia Zoo and the footage of their honeymoon -- which they spent trapping crocodiles -- formed the basis of his first "Crocodile Hunter'' documentary. They had two children, Bindi Sue and Robert Clarence.