Mainland outgun Japan in opening salvo of swimming supremacy battle

China drew first blood in their battle with Japan for Asian Games swimming supremacy, winning three golds to Japan's two on a sultry opening finals night at the Thammasat University aquatics complex.

The mainlanders - hoping to take the lion's share of the 32 golds on offer in Bangkok - got off to a flying start when Shan Ying swept to gold in the women's 100 metres before Zeng Qiliang powered home to finish first in the men's 100m breaststroke.

China sealed their gilt-edged evening with a typically dominant performance in the women's 4?200m freestyle relay, with the mainland's quartet finishing a full four seconds ahead of the second-placed Japanese.

But China's hopes of a clean sweep had been shattered earlier in the evening in the women's 400m individual medley as world record holder and reigning world champion Chen Yan slumped to third behind teammate Wu Yanyan in second and Japan's Yasuko Tajima, who took gold.

Chen, who smashed the world record for the distance at last year's All China Games in Shanghai when she clocked four minutes and 34.79 seconds, was close to 13 seconds off her mark as she trailed in in 4:47.34.

A Chinese swimming official later declined to comment on the dip in Chen's form when approached by a reporter. None of last night's medal winners held press conferences as dozens of journalists besieged organisers with complaints over facilities.