China won back-to-back gold medals on the second day of swimming action at the World Aquatics Championships as Qin Haiyang roared to victory in the men's 100 metres breaststroke while Zhang Yufei took the women's 100 metres butterfly title on Monday.

Qin set the second-fastest time in history behind Britain's world record holder Adam Peaty, finishing in 57.69 seconds with a three-way tie for the silver as Nicolo Martinenghi, Arno Kamminga and Nic Fink were all locked on 58.72 seconds.

The new champion, who took the lead at the first turn and never looked back, shaved 0.13 seconds off his previous Asian mark of 57.82 seconds which was set in the semi-finals.

"That is a pretty good time. That is my best time. But I can do better. I will catch up to the world record," Qin said of Peaty's 56.88 mark set at the 2019 worlds.

Zhang then came up with another dominating display to emerge triumphant in her event with a time of 56.12 seconds, finishing ahead of Tokyo Olympics gold medallist Margaret Mac Neil of Canada and 2022 champion Torri Huske of the United States.

The competitors were separated by only 0.77 seconds coming into the final and Zhang raised her level in the home stretch to edge out her illustrious rivals.

"This is my first gold medal at the world championships," said double Olympic champion Zhang, who has seven bronze medals at the worlds.

"This is my happy time. I just feel wonderful and amazing." (Reuters)