A polar bear attacked a woman at Berlin Zoo after she climbed a fence and jumped into its habitat during feeding time, police said.
Police did not say why the woman jumped into the enclosure. She had to climb over a fence, a line of prickly hedges and a wall to get in.
She suffered serious injuries after being bitten on her arms and legs.
The keepers' bravery was praised after they dragged the 32-year-old out of a moat for the animals. They had to shove the animal out of the way after one of four polar bears dived into the water and attacked her, inflicting serious bites to her legs and arms.
Knut, the zoo's baby bear that became an international celebrity in 2007 after it was hand-reared by a keeper, was in the enclosure at the time. Germany went polar bear crazy after the birth of the cute animal.
Last December a man who afterwards said he was "lonely" survived jumping into the same zoo enclosure when keepers diverted the bears with chunks of beef.
"The woman has proved herself to be careless by jumping into the enclosure," a police spokesman said afterwards. "Logic tells us that polar bears will do this type of thing in this situation."