Pan 100m world record ignites World Champs; Kim claims gold

China's wunderkind Pan Zhanle clinched the men's 100 metres freestyle world record on Sunday to ignite the opening day of the World Championships in Doha where Kim Woo-min claimed a surprise 400 freestyle title for South Korea.

Having flirted with the world record at his home Asian Games in Hangzhou last year, 19-year-old Pan clocked 46.80 seconds in a stunning leadoff swim in the 4x100m relay to eclipse the previous mark of 46.86 set by Romania's David Popovici.

"Breaking the world record is an honour for me," said Pan, who powered China to the relay title ahead of runners-up Italy and the United States.

"This is a motivation for both young and old swimmers. I believe I can go faster than today's time.

"It is truly a magical night."

Pan's swim at Doha's Aspire Dome pool makes him favourite for the individual 100 freestyle title and the gold medal at this year's Paris Olympics.

"I'm lucky to have awesome teammates and we did really well today. It's just the first day and I’ve been feeling very excited," he added.

"This is just a start... I’ll keep working hard for the Paris Olympics."

Kim upset a strong field for the 400 freestyle gold, charging out to a big lead midway through the final.

He held on grimly as Australian runner-up Elijah Winnington and German bronze-winner Lukas Maertens threatened to overhaul him in a fierce final-lap sprint.

The 23-year-old Kim clocked three minutes and 42.71 seconds to edge Winnington by 0.15s and shave more than a second off his personal best.

"I didn't expect to win a medal. I was just happy to be racing against these champions," Kim told reporters through an interpreter after emulating compatriot Park Tae-Hwan, a former 400m world champion.

"My main focus was the beginning of the race because I believe it's my strength. But now on I will have to focus on the second part."

Winnington, who won the world title in 2022, enjoyed a return to form in the leadup to Paris, having slumped to seventh at the World Championships in Fukuoka last July.

"I definitely came off the back of a very disappointing last year and to turn around this much in six months' time, I’m really happy," he told reporters.

"I’m in a really good head-space and that just proved it ... It’s the second best time of my career."

Kim was not the only surprise in the 400m. Olympic champion and Fukuoka runner-up Ahmed Hafnaoui bombed out in the preliminaries.

The Tunisian was 17th fastest in the heats and will hope for far better when he defends his 800m and 1 500m freestyle titles later in the meet.

Having missed Fukuoka while on a mental health break, world record holder Adam Peaty topped qualifying for the 100 metres breaststroke final with a time of 58.60 seconds, edging American Nic Fink by 0.13 seconds.

A slew of top swimmers have skipped Doha to focus on their Olympic preparations, but Briton Peaty is using the event as a stepping stone on the road to Paris where he will hope for a third successive 100m gold.

"Obviously we're coming off a very big winter so we're getting it flying again," Peaty told Reuters.

"I was just process-led, get the job done.

"Tonight I showed that I can still get it done."

New Zealander Erika Fairweather claimed the women's 400m freestyle title with a time of 3:59.49, blitzing a field lacking the power trio of world record holder Ariarne Titmus, Canadian sensation Summer McIntosh and American great Katie Ledecky.

Fairweather finished more than two seconds ahead of China's silver-winning Li Bingjie, with German Isabel Gose taking bronze.

With several of their best women skipping Doha, Australia missed out on a fourth consecutive 4x100m relay world title, finishing second behind the Netherlands (3:36.61).

American world champion Kate Douglass topped qualifying for the final of the women's 200m individual medley ahead of Canada's Sydney Pickrem.