Bronze medallist China's Lu Ying, gold medallist Sweden's Sarah Sjostrom and Silver medallist Denmark's Jeanette Ottesen (R-L) celebrate after the women's 100m butterfly final during the Aquatics World Championships in Kazan, Russia August 3, 2015.  [Photo/Agencies]

KAZAN - China pocketed a bronze on the second competition day of swimming at the Kazan worlds here on Monday, while three world records were smashed.

Sweden's Sarah Sjostrom defended her 100-meter butterfly title in 55.64 seconds when she broke the world record of the event for the second time in Kazan. She improved the previous world record, which was set by herself on Sunday's heats, by 0.1 second.

Denmark's veteran Jeanette Ottesen took the silver in 57.05, while China's Lu Ying came third in 57.48.

"I swam slower than I did in the semis earlier," said Lu, runner-up of the event at the London Olympic Games. "I expected a better time."

Hungary's swimming "Iron lady" Katinka Hosszu rewrote the women's 200m individual medley WR to 2:06.12, 0.03 second faster than the previous record set by American Ariana Kukors at 2009 Rome worlds.

Japanese Kanako Watanabe came second in 2:08.45, while British girl Siobhan Marie O'Connor came third in 2:08.77. China's Ye Shiwen, winner of the event at the London Games, only finished eighth.

Ye seemed exhausted after the final and left without a word.

The women's 1,500m freestyle world record was also renewed as American swimming star Katie Ledecky timed 15 minutes 27.71 seconds in the heats, shaving 0.65 seconds off the mark she set at the Pan Pacific championships in Australia in 2014.

"I'm in quite a bit of shock right now," Ledecky said. "I was barely even focusing on this morning's swim. I was so relaxed. I realized kind of toward the end because I could see people waving."

It's the fourth time Ledecky has broken the record in the 1,500m and she will have a chance to improve it again in Tuesday's final.

Britain won its first swimming gold in Kazan when the 20-year-old Adam Peaty touched first in the men's 100m breaststroke with 58.52. South Africa's Olympic champ Cameron Van Der Burgh trailed in 58.59, while Britain's Ross Murdoch third in 59.09.

France's Olympic champion Florent Manaudou showed his dominance of the men's 50m butterfly with a winning mark of 22.97. Brazil's Nicholas Santos came second in 23.09, while Hungary's Laszlo Cseh took a bronze in 23.15.

Also on Monday, China's swimming superstar Sun Yang, who led the 200m freestyle heats with a 1:46.00 finish, ranked fifth in the semifinal with 1;46.17. American star Ryan Lochte won the semis in 1:45.36.

"I think I will do better in tomorrow's final," said Sun, who won the 400m free on Sunday. "I expect a top three finish."

China's Fu Yuanhui ranked fourth in the women's 100m backstroke semifinal to reach the final, while Xu Jiayu qualified for the men's 100m back final with a sixth finish in the semifinal. Chinese girl Shi Jinglin also made the final of 100m breaststroke.