Japans Eriko Hirose (L) shakes hands with Chinas Wang Yihan after defeating her. - AFP Photo

“It is truly a memorable moment for me as this is my greatest ever achievement,” Hirose said.

“You do not often beat the world No. 1 and doing it at this level is really something I did not expect.”

In the men's singles, defending champion Lin Dan of China defeated compatriot Bao Chunlai 21-16, 21-13 in the third round.

Second-seeded Saina Nehwal of India became the favorite in the women's singles after beating Ella Diehl of Russia 21-14, 21-18 to move into the quarterfinals.

“Now, because I'm the second seed, it's tougher for me,” Nehwal said, “because I have to give more than 100 percent to win in every match.”

Wang had defeated Hirose in their three previous matches but, despite her top ranking, she has not won any tournament since November.

“I was surprised but Wang was not too consistent, so I knew it might be 50-50,” Nehwal said of the Wang-Hirose match.

“I was quite sure that Eriko could do it.”

The 20-year-old Nehwal has clinched three titles this year and is on a 17-match winning streak.

Cheng Shao-Chieh of Taiwan outlasted Juliane Schenk of Germany 19-21, 21-13, 21-19 to remain the only unseeded player in the women's singles tournament.

“Before, there were big differences in the way I play and the results,” said the girl with the dragon tattoo.

“Now I'm actually learning to control myself to have a more level game.”

Cheng has five tattoos, including a dragon on her left ankle, and won the Taipei Grand Prix this month.

Her career has been hampered by a nagging knee injury.

“It still affects me,” she said.

“It's not completely healed but I try not to think about it. I'm not in a wheelchair, so I'm going to keep on playing.”

Cheng may be short, listed at 1.58m on the website of the Badminton World Federation. She may be ranked only 46th in the world. But she has a 16-4 record this season and was successful on the big stage in the past.

She won the bronze medal at the 2005 worlds and became a junior world champion in 2004.

European champion Tine Baun of Denmark, Frenchwoman Pie Hongyan, and China's Lin Wang, Wang Shixian and Wang Xin also advanced.

Baun edged Petya Nedelcheva of Bulgaria 21-19, 23-21.

 “I still have my doubts,” said Baun, who was sidelined for four months by an injury.

“I wasn't playing my game. I was fighting.

“The next step in the quarterfinals is to let everything go and play what I can and see how far it gets me.”

In the men's tournament, top-ranked Lee Chong Wei of Malaysia, European champion Peter Gade of Denmark, Chen Jin of China and 2004 Olympic champion Taufik Hidayat of Indonesia also advanced.

Lee beat Rajiv Ouseph of England 21-9, 21-9, and Gade defeated Marc Zwiebler of Germany 21-14, 21-15.

The 13th-seeded Park Sung Hwan of South Korea and the unseeded Kazushi Yamada of Japan and Hsueh Hsuan Yi of Taiwan moved into the last eight, too.

Hsueh upset ninth-seeded Boonsak Ponsana of Thailand 21-13, 21-11. - AP