Japan's hopes of qualifying for this summer's Rio Olympics in women's football were left hanging by a thread after the medal contenders were ambushed 2-1 by China on Friday.

Goals from China's Zhang Rui and Gu Yasha sent the former world champions crashing to their second defeat in three matches at the round-robin qualifying tournament in Osaka, leaving them fifth of six teams on one point.

Meanwhile, Australia underlined their dominance by beating South Korea 2-0 to notch a perfect nine points from three games.

But the alarming slump in form of Japan's 'Nadeshiko' -- who are named after a frilly pink carnation -- has sparked dismay, with former superstar Homare Sawa accusing the players of lacking heart.

Japan beat the mighty United States to lift the World Cup in 2011 to provide a ray of light to a nation recovering from a deadly tsunami and the resulting nuclear crisis.

Norio Sasaki's side took silver behind the Americans at the 2012 Olympics in London and finished runners-up to their arch-rivals again at last year's World Cup in Canada.

They now need a miracle to qualify for Rio after the visiting Chinese outmuscled the Asian champions, leaving their players slumped on the turf sobbing uncontrollably at the final whistle.

They must beat Vietnam and then North Korea, in what will be a politically charged match, and hope other results go their way.

China, on seven points, North Korea (five) and South Korea (two) are all above Japan.

"I take full responsibility," Sasaki told reporters. "But we still have a chance so we will keep battling. We have to get ourselves back up mentally."