TOKYO - China's Zhang Yufei won her first Olympic gold in Tokyo, breaking the Olympic record in the women's 200m butterfly on Thursday.

Zhang led the field from the beginning, winning gold in two minutes and 03.86 seconds and slicing 0.2 seconds off the Olympic record set by compatriot Jiao Liuyang at London 2012.

This is the second medal for the 23-year-old, who claimed silver in the 100m butterfly earlier this week.

Americans Regan Smith (2:05.30) and Hali Flickinger (2:05.65) took silver and bronze respectively.

Later in the day, China also won its first gold in the women's 4x200m freestyle relay with a new world and Olympic record time of 7:40.33. Five-time event winners the United States had to settle for silver in 7:40.73, with former world record holders and Beijing 2008 winners Australia snaring bronze in 7:41.29.

In the first-ever Olympic men's 800m freestyle event, 21-year-old Robert Finke of the United States took the spoils in 7 minutes 41.87 seconds, ahead of Italy's Gregorio Paltrinieri and Mykhailo Romanchuk of Ukraine.

"The best time I had going in [before Tokyo 2020] was 7:47, and prelims I dropped down to 7:42 and here [in the final] I dropped another second. I had no idea I was going to do that," said Finke.

Caeleb Dressel won the U.S. a gold in the men's 100 freestyle with a new Olympic record time of 47.02, having also triumphed in the event at the World Championships in 2017 and 2019.

Australia's Rio 2016 winner Kyle Chalmers settled for silver in 47.08, while Russian Olympic Committee swimmer Kliment Kolesnikov took the bronze in 47.44.

Izaac Stubblety-Cook of Australia topped the podium in the men's 200m breaststroke with a time of 2:06.38.

"You can only be an underdog once and I had that luxury today. It was an experienced field, but I stepped it up through the heat and the semi. It was quite exciting to know I had more to give. I'm happy to be here but even happier with the result," said Stubblety-Cook.

Arno Kamminga of the Netherlands claimed silver in 2:07.01, ahead of bronze medalist Matti Mattsson of Finland in 2:07.13. All three swimmers outpaced the previous Olympic record time of 2:07.22, with world record holder Anton Chupkov only ranking fourth.

Emma McKeon of Australia qualified as the top seed for the women's 100m freestyle final, with Siobhan Haughey from China's Hong Kong qualifying second and lowering her own Asian record time to 52.40.

The finalists have also been set in the men's 200 backstroke, women's 200m breaststroke, and men's 200m individual medley. Wang Shun of China led the finalists in men's 200m individual medley with 1:56.22.