Athens Olympian Vladislav Polyakov overcame Athens champion Kosuke Kitajima in the 50m breaststroke to bring Kazakhstan the first swimming gold in Doha Asian Games where China and Japan shared lead on the second day in the aquatic center.

China and Japan each had two gold medals to their names while South Korea bagged one through their promising star Park Tae Hwan.

Polyakov, fifth place finisher in the Athens Olympics, pulled off the title in 28.29 seconds before Kitajima, 100m and 200m breaststroke winner in Athens, bagged silver with nine hundredths of a second behind.

The 50m event was newly added to the Asian Games program and Kitajima will defend his 100m and 200m crowns after he eased to the 200m gold with a then world record time of 2:09.97. Wang Haibo from China came third in 28.41.

"This is absolutely an unexpected victory for me as Japanese Kitajima is very strong. It is always nice to beat an Olympic champion, but this not his prime event, not mine either. So I was surprised when I turned around that everyone was so close," said the 23-year-old Polyakov.

Park rushed to the gold in the men's 200m freestyle in an Asian record, claiming the first swimming gold for his country in Doha in 1:47.12, beating his own previous Asian best created in August by 0.39 seconds.

Zhang Lin from China settled for silver in 1:47.85 while Daisuke Hosokawa of Japan took bronze in 1:49.62.

Park and Zhang are expected to compete against each other again in the 400m and 1,500m freestyle.

The last time the two raced together in the 200m free was at the 2006 Pan Pacific championships, where Park got a sliver ahead of Zhang but the two were separated by just eight hundredths of a second.

"My strategy was OK but my turning technique was not as good as Park's," said Zhang. "When I turned for the last 50 meters, I found he had led me by half a body-length."

"It was a pity that I did not win but my focus will be the Beijing Olympics," he added.

China lifted women's 4x100m freestyle relay title for the fifth time in six Asian Games, the second relay gold following the women's 4x100m medley relay victory in 3:42.11.

Japan were promoted to the second place in a time of 3:45.86 after South Korea suffered disqualification.

Hong Kong of China, clocking 3:48:82 and originally fourth, took bronze, their first swimming medal in Doha.

"We feel very lucky to get the bronze after South Korea got a DQ. We hope we can keep the luck for the next four days and hopefully get another medal," said Tsai Hiu Wai Sherry.

Defending champion Qi Hui of China, reigning 400 IM short course world champion, sailed to the victory of women's 400m individual medley in 1:38.31.

"I don't think tonight's competition is tough for me," said the21-year-old Qi. The result is about three seconds slower than her personal best.

"The result is so-so for me but I still hope to set a personal best in the Asian Games," she said.

Qi, the 200m breaststroke specialist, is expected to defend her title here next week.

Chinese teenager Yu Rui finished as somehow a surprise silver medallist as the 17-year-old clocked 4:39.51 in her first Asian Games. Maiko Fujino, fifth-placed in last year's world championships, was third in 4:42.70.

Defending champion Takashi Yamamoto came from behind to grab the men's 100m butterfly gold as the silver medallist in the 200m fly in the Athens Olympics clocked 52.54 to become the first male swimmer to triumph in the same event for three consecutive times in Asian Games.

His teammate Ryo Takayasu took silver in 52.84 while Chinese Wang Dong settled for the third in 53.03.

Reiko Nakamura eased to defend her 200m backstroke to give Japan the second swimming gold of the night when the 2006 Pan Pacific champion clocked a winning time of 2:10.33.

Chinese youngster Zhao Jing, 16, came second in 2:11.54, ahead of Japanese Takami Igarashi, who finished third in 2:12.55.