With two titles in hands, China's Xu Jiayu and Zhang Yufei both became double winners on the first day of the FINA/airweave Swimming World Cup 2017 at the National Aquatic Center (Water Cube) here on Friday, while World champions Chad Le Clos of South Africa and Katinka Hosszu of Hungary also grabbed two gold medals apiece.

Newly crowned World champion Xu Jiayu showed his excellent start and turn skills by winning the men's 50m backstroke in 23.09 seconds, ahead of Pavel Sankovich of Belarus 23.11 and Junya Koga of Japan 23.34.

Xu later joined the winning team in the mixed 4X50m medley relay, together with Yan Zibei, Zhang Yufei and Liu Xiang 1:39.10, beating Australia and the Netherlands into second and third, respectively.

"It was a great challenge for me that I swam three finals tonight, since I did not train very much these days. I took the advantage of my start and turn skills with under-water dolphine kicks. I was really exhausted, "said Xu, who also finished third in 100m butterfly, well behind the champion Le Clos.

Le Clos dominated the men's 200m freestyle in 1:41.81 and the 100m butterfly 49.18.

"Today was great. I have competed in Beijing for many years since 2011. It is a great pool that I was happy to win tonight. In fact I was a little bit nervous because I had a long travel to Beijing. I just arrived a day ago. I really did not know whether I was fit or not for the competition. I guess I will be better tomorrow, and better in Tokyo and Singapore. I need a fews days to get used to the Asian time," Le Clos said.

Le Clos also gave a big thumb up to the new competition format of the World Cup introduced this year.

"I like it very much, because everybody has the opportunity to win. That means more people could win and it would be more difficult to win. It makes the competition more competitive."

Olympic and World champion Hosszu snatched victories in the women's 100m backstroke (56.34) and the 100m Individual medley (57.50).

"I love to come back here to Beijing and I like the audience very much. I could see some fans carrying the Hungarian national flags. I did not take a break after the World Championships. I kept training and competing. I look forward to compete in the European Championships as my next goal," said the Iron Lady.

The 15-year-old Wang Jianjiahe of China set a new Junior World Record in the women's 400m freestyle (3:59.69), followed by world silver medallist Li Bingjie (4:01.75).

"I did not expect to break the world junior record at all. I need to improve my turns in the future," Wang said.

Sarah Sjostrom of Sweden was happy with her time of 23.40 as she won the 50m freestyle, beating Ranomi Kromowidjojo of the Netherlands (23.47) and Cate Campbell of Australia (23.67).

"I am happy with my swim here. I feel a bit tired coming into this World Cup. So I did have very high expectations.”

Daiya Seto of Japan broke the meet record in the men's 400m individual medley in 3:58.20. The previous mark was 3:58.69 held by Thomas Fraser-Holmes of Australia in 2014. In other events, Zhang Yufei clocked 2:05.02 to win the women's 200m butterfly, Yasuhiro Koseki of Japan claimed victory in men's 200m breaststroke (2:03.43) and Alia Atkinson (JAM) took the title in the women's 50m breaststroke (29.57).

The 2017 FINA/airweave Swimming World Cup is made up of eight stops and Beijing is the sixth, ahead of the last two stops in Tokyo and Singapore.