Incheon:
Chinese swimming superstar Sun Yang stormed past his rivals to an emphatic 400 metres freestyle win on Tuesday as the Asian Games was rocked by its first positive drugs test.
The world and Olympic champion hit back from his shock 200m loss to Kosuke Hagino as he dominated the Japanese and South Korea's Park Tae-Hwan, winning comfortably by 1.3 seconds.
Sun roared in celebration at the win, among five for China on the night as they finally hit form in the pool and leapt ahead of Japan 10-7 in the swimming titles tally.
It completed a triumphant day for Asia's powerhouse, which has long dominated the regional Olympics and has now accumulated 39 gold medals, more than double the 17 gathered by second-placed South Korea.
There was controversy elsewhere after it emerged that a footballer from Tajikistan had become the first athlete at the Incheon Games to fail a doping test.
"It's a confirmed case," a source told AFP, adding that the as yet unidentified player would be kicked out of tournament.
The Central Asian republic are due to play Iraq in the second round of the men's football on Thursday. The doping case comes after two incidents of alleged sexual assault at the Games, involving an Iranian football official and a member of the Palestinian team.
Sun, who blamed a thumb injury for his 200m loss to Hagino, strolled out for the race wearing a pair of gold headphones and he kept his cool when Hagino shot out to an early lead.
The towering Chinese reeled him in by the halfway mark and powered away over the second 200m to take Park's Asiad crown, as he did in the same event at the 2012 Olympics.
Olympic champion Ye Shiwen crushed the competition in the women's 400m medley, Ning Zetao won the men's 50m freestyle and Chen Xinyi won the women's 100m butterfly before China's women finished off with 4x200m freestyle gold.
