A two-year-old Chinese girl left unattended fell 10 floors from her family's apartment window and survived after being caught by a woman passing by, state media has reported.

The toddler is in critical condition with internal bleeding and other unspecified injuries while the woman who saved her suffered a broken arm, China Central Television and the Xinhua News Agency said.

The girl, named Zhang Fangyu but known by the nickname Niu Niu, was in the care of her grandmother when the older woman left the 10th-floor apartment outside the eastern city of Hangzhou to run an errand, CCTV said.

Neighbours saw Niu Niu dangling from the apartment window for several minutes, Xinhua said, and when the girl fell, Wu Juping "kicked off her high-heeled shoes" and ran to catch the child.

"It was so urgent. I saw her when she was about to fall and rushed there, and after tens of seconds she fell off," CCTV quoted Ms Wu as saying.

A 31-year-old mother, Ms Wu told CCTV that when she saw the hanging girl she thought of her own seven-month-old son who had once fallen from a high chair and cut his mouth: "I thought to myself 'I should stretch my arms to her. Because I am right here, I must get her.' Then I made it. I caught her in my arms."

The impact knocked Ms Wu out and sent her crumbling to the ground along with breaking her left arm, the reports said.

CCTV quoted a doctor as saying a scan showed no damage to Niu Niu's brain but that the girl's abdomen was swollen in a sign of possible injury to organs.