REYKJAVIK - Bobby Fischer, America's first and only world chess champion who was once dubbed the "Mozart of Chess", has died in Iceland at the age of 64.

A spokesman for Fischer, who could have faced prison in America for violating sanctions against former Yugoslavia by playing a chess match there, confirmed that he had died. The cause of death was not immediately made public.

Fischer, a former child prodigy who once said he liked to watch his opponents squirm and who had become an Icelandic citizen, became world champion by beating the Soviet Union's Boris Spassky under the glare of Cold War publicity in Reykjavik in 1972.

The brilliant but eccentric American abandoned his title without moving a pawn by failing to meet a deadline to defend his crown in Manila in 1975. World chess authorities reluctantly awarded it to challenger Anatoly Karpov of the Soviet Union, who was to hold it for the next decade.

Fischer withdrew into himself, not playing in public and living on little more than the magic of his name, although millions of enthusiasts regarded him as the king of chess.

He made headlines and fell foul of U.S. authorities when he came out of seclusion to play his old rival Spassky in Yugoslavia in 1992, at a time when the country was the target of sanctions during Belgrade's war with breakaway republics.

He vanished after the match, for which he won $3 million (1.5 million pounds), and resurfaced only after the September 11, 2001, attacks in the United States. In an interview with a Philippine radio station, Fischer praised the strikes and said he wanted to see America "wiped out".

Fischer, who also stirred controversy with anti-Semitic remarks, was granted Icelandic citizenship in March 2005 after eight months in detention in Japan fighting a U.S. deportation order.

"THE MOZART OF CHESS"

Fischer always had a high opinion of himself. Asked who was the greatest player in the world, he once replied:

"It's nice to be modest, but it would be stupid if I did not tell the truth. It is Fischer."

It was not an idle claim. Arguably the greatest natural chess genius the world has seen, he was called "the Mozart of chess" when he began winning at the age of six.

His success soon gained Fischer a reputation for being cocky. He told interviewers his favourite moment was when opponents began to feel they would lose. "I like to see 'em squirm," he said.

He was U.S. junior champion at 13 and U.S. Open champion at 14, retaining the title whenever he chose to defend it.

He was the youngest international grandmaster ever at 15, gaining the rating at his first international tournament in Yugoslavia. He once defeated 21 grandmasters in succession - no U.S. player had beaten more than seven in a row.

As Fischer's fame grew, his temperament became more unpredictable. He walked out of tournaments because of what he considered to be bad lighting or bad air conditioning. He refused to play matches on Saturday, the Jewish Sabbath.

In the mid-1960s, he opted out of two world championship qualifying series because he thought the tournament system favoured the Russians. In 1967, when officials would not meet his demands for better conditions, Fischer angrily withdrew from international competition "for a period of introspection".

He took his massive collection of chess books and moved to California, where he later said he had "plotted my revenge if I ever came back".

When the rules were changed in 1972 to include an eight-player eliminator to find the challenger to world champion Spassky, Fischer had the chance to prove he was as good as he always said he was.

He raced to victory in the candidates' series, prompting Spassky to say the American would find a world championship series a different and more difficult proposition. He was wrong.

If anyone suffered from the pressure when the match was held in Reykjavik, Iceland, it was Spassky.

He became a national hero - Americans who had never played chess and knew little about the game followed the Fischer saga.

In the 1990s, he was said to be living under assumed names in cheap hotels in Pasadena on the outskirts of Los Angeles, surviving mainly on occasional royalties from his books. In London, one newspaper described him as "dressed like a derelict, waddling and fat and with a straggly beard".

Former friends painted a picture of a solitary man spending much of his day in rooms littered with chess books, oranges and jars of vitamins, playing chess by himself and reading magazines on chess to keep in touch.

One commentator said there was one constant through his life's exceptional peaks and troughs - his "running battle with the rest of the human race".