The 55-year-old worker was killed in the southern city of Stavropol, RIA Novosti reported Wednesday.
"A zoo cage cleaner forgot to lock the bear's cage, and the animal attacked him from behind," Boris Skripka, an official of the city's emergency services, said. "The bear caught him by the leg and damaged a vital artery. The worker was rescued by other zoo employees, but succumbed to his injuries before the ambulance arrived."
The bear is still being kept at the zoo while zoo and city officials decide its future.
"I have no idea of what should be done with animals under such circumstances," zoo spokesman Sergei Vedeneyev said.