The announcement by the Russian grandmaster - the world's No. 1-ranked chess player since 1984 who is considered by some the best in the history of the game - came shortly after he won the 14-match Linares tournament in Spain on Thursday, despite losing the final game.

''Before this tournament, I made a conscious decision that Linares 2005 will be my last professional [tournament], and today I played my last professional game,'' Kasparov said at a news conference, according to a video posted on the online chess magazine http://www.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, and quickly cut a swath through the chess world with an aggressive style that shunned settling for a draw. He said part of the reason he was retiring was because he saw no real goals left to accomplish in professional chess.

He said Friday he wanted to concentrate more on politics in Russia. He has emerged as an outspoken critic of President Vladimir Putin and is playing a leading role in the Committee 2008: Free Choice, a group formed by prominent liberal opposition leaders.

''As a chess player, I did everything I could, even more. Now I want to use my intellect and strategic thinking in Russian politics,'' Kasparov said Friday.

''I will do everything in my power to resist Putin's dictatorship. It is very difficult to play for a country whose authorities are anti-democratic,'' he said..

Born in Baku in the then-Soviet republic of Azerbaijan, Kasparov is thought by many to be the best chess player ever.