Australians Matt Welsh and Leisel Jones claimed the first two and Japan's Kosuke Kitajima concluded the hectic spree with the third in the men's 100 metres breaststroke.

Welsh, best known as a backstroker, caused the biggest shock at the Palau Sant Jordi when he broke the men's 50 metres butterfly world record in an inspired sprint which caught his rivals cold.

Welsh, the slowest final qualifier, got out fast and blasted away from his more fancied rivals down the outside lane number eight, hitting the wall in 23.43 seconds, 0.01 seconds inside the mark set by fellow Australian Geoff Huegill at the 2001 world championships.

American Ian Crocker, the fastest man in the heats and semi-finals, had to settle for silver in 23.62 with Russia's Yevgeny Korotychkin third in 23.73.

"Oh my God, I've won. Oh my God, it's a world record," said Welsh. "Damn, I've got another race," he added, reminding himself that he had a semi-final to come in his 100 backstroke title defence. He successfully negotiated that to qualify joint fourth-fastest overall for Tuesday's final.

Jones, Olympic and world silver medallist, plucked her world record out of the semi-finals, sweeping through the 100 breaststroke in one minute 06.37 seconds to beat the 1:06.52 mark set by South Africa' Penny Heyns in 1999.

POWERFUL FINISH

Kitajima trailed sixth at the halfway mark of the 100 breaststroke final as Britain' James Gibson led inside the world record split.

But the double Asian champion hit back with a vengeance on the return leg to win in 59.78 and better the 59.94 mark set by Russia' Roman Sludnov two years ago.

Thirty-year-old Jenny Thompson struck a blow for swimming's older generation when she rippled away with her second gold medal in two days, taking her overall world championship medal tally to a record 11 -- seven gold, three silver and one bronze.

Thompson, who anchored the U.S. to victory in Sunday's 4x100 freestyle relay, trailed at the halfway mark of the 100 butterfly final but surged through on the return length to regain the title she won in 1998.

Thompson, world 100 butterfly and 100 freestyle champion in 1998, was chased home by Poland's Otylia Jedrzejczak (58.22) and Slovakia's Martina Moravcova (58.24) but they could not catch the American, who is enjoying a triumphant comeback after retiring following the 2000 Olympics.

Medical student Thompson, who won a title at the Pan-American Games way back in 1987 when she was just 14, said that the idea of winning world gold 16 years later would have seemed unbelievable.

Fellow American Natalie Coughlin, suffering from a high temperature and eliminated in the morning's heats of her 100 backstroke title defence, trailed home last.

TOOK CHARGE

Kitajima had come within 0.04 seconds of the world mark in Sunday's semi-finals when he clocked 59.98 to become only the second man to swim the event in under a minute and he took charge of the final with a rip-roaring finish.

American Brendan Hansen took the silver in 1:00.21, almost half a second adrift, and Gibson had to settle for bronze in 1:00.37.

Olympic champion Yana Klochkova scored a runaway victory in the women's 200 individual medley after suffering a rare defeat in the event at the 2001 worlds at the hands of American Maggie Bowen.

The 20-year-old Ukrainian won by fully two seconds in a championship record 2:10.75 from Australia's Alice Mills (2:12.75) and China's Zhou Yafei (2:12.92). Bowen was fifth.

For once, Ian Thorpe was upstaged on a night when the record-breaking fell to others.

The 20-year-old Australian, who scored a unique third successive win in the 400 freestyle on Sunday to take his overall world gold tally to a record nine, was second best to his Dutch rival Pieter van den Hoogenband in both heats and semi-finals of his 200 freestyle title defence.

But Tuesday's final showdown between Thorpe and his Olympic conqueror will be the one that counts.