China's 13-year-old swimming prodigy Yu Zidi makes waves at Asian Games

A 13-year-old swimmer from China has kicked off the 20th Asian Games in blistering form.

Yu Zidi, who does not turn 14 until next month, was fastest by far in the women's 200m butterfly heats.

The Games, being held in Japan, were officially declared open on Saturday by Japan's Emperor Naruhito although there were a large number of empty seats at the 30,000-capacity stadium in Nagoya.

It sounded the starting pistol on two weeks of intense action as the continent's finest athletes compete in more than 40 sports before the curtain comes down on October 4. As always at the Asian Games — which started in 1951 — Olympic staples such as athletics and swimming will sit side-by-side with regional favourites like sepak takraw and kabaddi.

In the swimming pool, Chinese teenager Yu touched almost 2.70 seconds ahead of compatriot Chang Mohan in the butterfly heats and will be a hot favourite to take her first major gold in Sunday evening's final.

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China's men's 100m freestyle world record holder and Olympic champion Pan Zhanle also went through fastest to the final in 48.07sec, but was only 0.06sec quicker than South Korea's Hwang Sun-woo.

Meanwhile the first gold medal of the 20th Asian Games was won on Sunday by host nation Japan when Takumi Hojo won the men's individual triathlon in Gamagori city near Nagoya with China's Zhang Xirui second and Kazakhstan's Arlan Zhanabay taking bronze.

It was the first of 469 gold medals to be awarded at a two-week spectacle that has more athletes than the Olympics.

Hojo finished the 750m swim, 20km bike ride and 5,000m run in 52min 56sec, nine seconds clear of Zhang with Zhanabay a further six seconds behind in third.

"As it's our first gold medal, it's given the Japanese team a real boost," said the 30-year-old Hojo, whose win will qualify him for the 2028 Olympics in Los Angeles.

"I was really fired-up. Even the rain held off, and I was in top form right up until I stood on the starting line."

China turned the tables later in the women's individual triathlon, where Lin Xinyu improved on her silver medal at the last Asian Games in Hangzhou by winning in 57min 37sec.

Huang Anqi completed a China one-two, 21 seconds behind, with Japan's Manami Hayashi taking the bronze in 58:36.