The Chinese, who roared out of the starting block on Saturday with four titles on the first day of competition, won their latest gold when female judoka Xian Dongmei beat Japan's Yuki Yokosawa in the 52 kg category.
Japan's Masato Uchishiba won the under 66 kg judo gold at the Olympics on Sunday after his usually dominant nation had not won a medal in the class in six Olympics and world championships since 1996.
In the pool, Japan's Kosuke Kitajima ruined American Brendan Hansen's 23rd birthday party when he beat him to win the men's 100 metres breast stroke title.
Kitajima, also the world champion, glided past the world record-holder Hansen on the last lap to give Asia its first male Olympic swimming gold since 1988.
"I feel good, super good," Kitajima said. "I knew from before the race that it would be a battle with Hansen, so I stepped on the starting block with a strong feeling that I'll definitely beat him mentally."
After two full days of competition, China led the medals table with five golds, two silvers and a bronze. Australia had four golds, a silver and three bronzes -- followed by Japan, with four golds and a silver.
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Xian became the first person to defeat a Japanese judoka at the Athens Games when she took the women's under 52 kg title by pinning Yokosawa to the mat for 25 seconds just over a minute into the final.
"This may be the last gold medal for me in world top-level judo competitions as I am nearly 30 years old now," said Xian, 29, who missed the Atlanta and Sydney Games because of knee injuries.
"Before coming to Athens, the Chinese judo team set the target of at least one gold," said Xian's coach Fu Guoyi, adding that Xian's win would inspire more Chinese to seek judo gold.
In their best Olympics start, China grabbed four golds on Saturday, winning the women's 10-metre air rifle, the men's 10-metre air pistol event, the women's synchronised three-metre springboard and the men's synchronised 10-metre platform.
Japan's Tadahiro Nomura became the first judoka to win gold in three consecutive Games when he beat Georgian Nestor Khergiani on Saturday. The 66 kg legend's compatriot Ryoko Tani became the first woman to win two Olympic titles in judo.
The Chinese are eyeing a big medals haul on Monday, with diving hopefuls Lao Lishi and Li Ting in the women's synchronised 10-metre platform and Peng Bo and Wang Kenan in the men's synchronised three-metre springboard.
China are also looking to their men's gymnastics team on Monday, and expect men's 62 kg weightlifters Shi Zhiyoung and Le Maosheng and women's 58 kg lifter Chen Yaqing to haul home gold.
