Ian Thorpe added another chapter to his burgeoning legend at the World Championships in Fukuoka, Japan yesterday when he shattered his 800 metres free-style world record, sharing the night with 16-year-old American Michael Phelps who smashed his 200 metres butterfly mark.

The Australian's time to win the World Championship title was all the more remarkable in that he did it just 30 minutes after swimming a competitive 200 metres free-style semi-final.

And it wasn't just shaving the record. He obliterated it, touching in seven minutes 39.16 seconds to beat the time he set earlier this year of 7:41.59. "I wasn't sure what I was able to do after the 200 and I tried to make it as easy as possible for myself to be able to swim another 800 as well and conserve part of my energy," he said.

"It turned out that I really did make it. I swam probably the fastest 600 of my life." Asked where he goes from here, he said: "I don't know where the line is in the sand. If there is one I would like to find it and jump over it."

Grant Hackett led the race for 700 metres until Thorpe turned on his last lap sprint. The 1,500 metres specialist clocked 7:40.34, the second fastest time ever and under Thorpe's old world record time.

"I was trying to nudge ahead but Ian kept sticking there like glue," he said. "I knew I had a good chance. I just went out there to give it a shot.

"Ian is a phenomenal competitor but he's not kicking away like he used to. We'll both be faster again next time."

It was Thorpe's 15th world record and his second in Fukuoka after his exploits in the 400 metres on Sunday. He swims the 200 metres final today. Hackett now has two silvers but will almost certainly take gold when he races the 1,500 metres on Sunday. Britain's Graeme Smith took bronze in the 800 metres yesterday.

Thorpe had to share the limelight though. Phelps, who burst onto the swimming scene earlier this year with a 200 metres butterfly world record, continued pushing the limits in the finals.

The American rewrote the history books with a scintillating display.

He hit the wall in 1:54.58, beating countryman Thomas Malchow and the old record of 1:54.92.

Anatoli Poliakov of Russia took the bronze.

"I'm just out there to do my best, to represent my country," the youngster said. "I went in feeling iffy but I wanted to see if I could hang on and I did. I just kept trying to hit my head on the wall.

"My adrenalin, I can't explain it. I'm so happy. I just wanted to go out there and get my hand on a world first. It's great for Americans. We just keep getting farther and farther ahead."

Roman Sloudnov stole the 100 metres breaststroke title, hammering another nail into American Ed Moses's coffin. The Russian couldn't match his sub-one minute semi-final time but was a happy man.

"I can swim a 59," he said. "I didn't sleep much because I was so excited and wasn't properly prepared for another world record but this was an interesting race until the last second."

Sloudnov set a new record on Monday of 59.94 and is the only man below one minute.

Moses, who held the record until Sloudnov snatched it from him earlier this year, could only manage third, behind Italian Domenico Fioravanti, the Olympic gold medallist.

"I was a little tired in the last 10 metres and I'm a little disappointed but I will try to keep my condition and do my best in my remaining races," he said. The fourth world title decided yesterday went to Haley Cope of the US who won the women's 50 metres backstroke. Antje Buschschulte of Germany was second and Natalie Coughlin of the US was third.

In other action, Inge de Bruijn made her Fukuoka debut and cruised through the 100 metres freestyle heats. She was the only qualifier below 55 seconds and is hot favourite to take the title today.

China's Luo Xuejuan was under world record pace for the first 150 metres of her 200 metres breaststroke semi-final but eased to touch in 2:26.03. In an earlier heat Romania's Beatrice Caslaru set a championship record of 2:25.45.