Blake, 53, was on a worldwide expedition to monitor global warming and pollution aboard his 119-foot yacht, said Alan Sefton, spokesman for Blake's organization, blakexpeditions.

The vessel, called Seamaster, was in the mouth of the Amazon on Wednesday night near Macapa, a city 1,600 miles north of Sao Paulo, when three or four assailants approached in a rubber dinghy ``commonly used by river rats that ply the Amazon river in search of victims,'' said state police chief Rosilene Martins de Sena.

``Armed and hooded individuals came over the rail and had the crew at gunpoint,'' Sefton said Thursday in a telephone interview. ``It would appear that Peter was down below and heard what was going on and came charging up'' and was shot at least twice.

Two crew members were slightly injured but have been released from the hospital.

Federal prosecutor Manoel Pastana told reporters the crew was preparing a barbecue on the yacht when the gunmen appeared, shouting ``Money! Money!''

According to local media, the killers took a spare engine and several watches from the Seamaster, which had been awaiting customs clearance to leave Brazil after a two-month stay.

Blake and a crew of 10 arrived in Brazil in October. Sefton said they spent two months in the upper reaches of the Amazon and Rio Negro and had encountered nothing but ``friendly, warm, hospitable people.''

``And as soon as the boat gets back into so-called civilization, something tragic happens,'' Sefton told New Zealand's One News television station.

New Zealand Prime Minister Helen Clark described Blake as ``a national hero,'' and flags were at half-staff across the country. Parliament paid tribute to Blake with a moment of silence and a native Maori hymn.

``I think he is to the waters what Sir Edmund Hillary (conqueror of Mount Everest) has been to the mountains. He's just the most amazingly accomplished yachtsman,'' Clark said. ``He was an inspiration to all New Zealanders, and we will all feel a tremendous sense of loss.''

New Zealand Ambassador Denise Almao flew into Amapa, the governor's office said in a note.

President Fernando Henrique Cardoso, the statement added, ``has ordered that the criminals be promptly identified and arrested.''

Seamaster had been scheduled to sail up the coast to Venezuela to meet blakeexpedition's jungle team. The vessel had previously been on a three-month study of wildlife in the Antarctic region.

American skipper Dennis Conner, a three-time America's Cup winner who was beaten by Team New Zealand 5-0 in 1995, praised Blake.

``He was a hero and role model for the New Zealand people and obviously a winner that was focused and accomplished his goals, whether it was winning the round-the-world race or the America's Cup,'' Conner said Thursday.

In March 2000, Blake said he had received letters from someone threatening to kill him and harm his family.

``We've always got crank mail, but it has been going beyond that recently,'' Blake said at the time. ``So we have taken all the precautions we were advised to take.''

After Blake's 1995 America's Cup win, Governor General Dame Cath Tizard said it was New Zealand's proudest day since Auckland native Edmund Hillary became the first man to climb Mount Everest in 1953.

The America's Cup was the only major sailing trophy that the self-proclaimed ``Nation of Sailors'' hadn't claimed, and Team New Zealand under Blake won with one of the most dominating performances in America's Cup history.

Blake was appointed in July as a goodwill ambassador of the United Nations Environment Program. Before that, he headed the Cousteau Society, an environmental group founded in 1973 by the late undersea explorer Jacques Cousteau.

Sefton said Blake considered the current expedition his last and greatest adventure, hoping to create greater awareness of the need to take care of the environment.

Blake, born in Auckland, announced earlier this year that he was relinquishing control of the New Zealand syndicate. He was knighted in 1995.  Blake, who began sailing at age 5, won the Whitbread Round the World Race in 1989 and took the Jules Verne Trophy in 1994 by sailing nonstop around the globe on a catamaran in 74 days, 22 hours, 17 minutes and 22 seconds. The record fell three years later.

Last year, he led the first non-American entry to retain the America's Cup in 149 years, beating Italian challenger Prada 5-0.