Britain' s Guy beat Sun Yang in 200m free

Britain's James Guy celebrates with his gold medal after winning the men's 200m freestyle final at the Aquatics World Championships in Kazan, Russia, August 4, 2015. [Photo/Agencies]

The men's 50m breaststroke world record was also a little fragile as it has fallen twice on Tuesday. The 20-year-old British swimmer Adam Peaty swam 26.42 in the semifinals to rewrite South African Cameron Van Der Burgh's previous mark 26.62, which was set in the heats earlier Tuesday.

"I knew there was something in there, but I decided to just stay relaxed and enjoy the environment," said Peaty, winner of the 100m breaststroke.

Australia got an 1-2 finish in the women's 100m backstroke as Emily Seebohm clinched the gold in 58.26 and Madison Wilson came second in 58.75. Mie Oe Nielsen of Denmark settled for bronze in 58.86. China's Fu Yuanhui finished fourth in a personal best time of 59.02.

Thanks to Mitchell Larkin, Australia won its first gold medal in men's event at Kazan worlds. Larkin timed 52.40 to win the 100m back, trailed by French Camille Lacourt, who touched in 52.48. The bronze went to Matt Grevers of the United States in 52.66. China's Xu Jiayu came fourth in 52.89.

The host won its first swimming gold on Tuesday as Yuliya Efimova beat Olympic champion Ruta Meilutyte of Lithuania to win the women's 100m breaststroke in 1:05.66. Meilutyte, world record holder of the event, trailed in 1:06.36. Alia Atkinson of Jamaica came third in 1:06.42.

Also on Tuesday, China's Youth Olympic champion Shen Duo reached the women's 200m free final with a third finish in 1:56.44. The race was led by Italian Olympic champion Federica Pellegrini, who touched first in 1:56.23. American star Missy Franklin ranked second in 1:56.37.