FUKUOKA, Japan Teenagers Ian Thorpe and Michael Phelps both set world records at the Swimming World Championships on Tuesday.

Australian Thorpe sliced almost two and a half seconds off his old world record to set a new standard of seven minutes 39.16 seconds to win the 800 meters freestyle final.

Phelps, of the United States, followed Thorpe's lead by breaking his own world record for the 200 meters butterfly, stopping the clock at 1:54.58, a third of a second better than his previous mark.

Russia's Roman Sludnov won the men's 100 meters breaststroke gold as expected, but failed to better the world record he had set 24 hours earlier, while American Haley Cope won the inaugural women's 50 meters backstroke title.

Thorpe, 18, claimed his third gold medal and set his second world record in three days when he won a great duel with fellow Australian Grant Hackett.

Thorpe, who had swum the 200 meters freestyle semifinals less than 20 minutes before he dived in for the 800, cut loose on the last length of the 16-length race to wipe 2.43 seconds off the previous mark of 7:41.59 which he set at the Australian trials in March.

Hackett also went under the old mark but had to settle for silver in 7:40.34 while Britain's Graeme Smith took the bronze in 7:51.12, Reuters said.

Sixteen-year-old Phelps swept along inside world record schedule all the way and denied fellow American and Olympic champion Tom Malchow's challenge to win in one minute 54.58 seconds.