Garry Kasparov (search), the world's No. 1 ranked chess (search) player since 1984 who some believe is the best in the history of the game, said on Thursday that he was retiring from professional play.

The announcement came shortly after he lost the final game of the 14-match Linares tournament, which he won.

"Before this tournament I made a conscious decision that Linares 2005 (search) will be my last professional (tournament), and today I played my last professional game," Kasparov said at a press conference, according to a video posted on the online chess magazine chessbase.com.

He said his last games were "very difficult for me to play under such pressure, because I knew it was the end of the career which I could be proud of."

Kasparov, 41, became the youngest world champion ever at age 22. He said part of the reason he was retiring was because he saw no real goals left to accomplish in professional chess.

The Azerbaijan-born Kasparov is thought by many to be the best chess player in history. But he will be remembered in part for one of his losses, a 1997 match against IBM supercomputer Deep Blue that was seen by some as a watershed moment in technological advancement.

In 2003, Kasparov averted a similar defeat when he agreed to a draw in the last game of his series against Deep Junior, which could process 3 million chess moves per second. The six-game series, dubbed Man vs. Machine, finished tied 3-3.

Kasparov's chess talent was apparent at an early age. In 1973 he attended the Botvinnik Chess School. In 1975 at the age of 12 he became the youngest ever player to win the USSR Junior Championship. At 16 he won the World Junior Championship. He achieved the title of grandmaster on his 17th birthday.

His first title match, from September 1984 to February 1985 against Anatoly Karpov was the longest in chess history. After 48 games, the psychological and physical strain on Karpov, who was leading but appeared likely to lose, caused chess authorities to end the match inconclusively amid controversy.

Kasparov won a rematch six months later, becoming the youngest world champion ever. He defended his title against Karpov in 1986, 1987 and 1990.