Russian media reported Wednesday that the exhausted-looking animal apparently traveled from Chukotka to the village of Tilichiki on Kamchatka, some 700 kilometers (434 miles) south.
Environmentalists said the bear could have lost its sense of direction while drifting on an ice floe.
Locals were making the bear feel welcome, giving it fish, media reported.
Videos posted online showed the animal moving past residents, showing no aggression.
Authorities in Kamchatka are preparing a rescue effort later this week. They plan to use a sedative to put the bear to sleep and then airlift it to Chukotka in a helicopter.
Polar bears dependence on sea ice makes them highly vulnerable to global warming. Shrinking Arctic ice cover could increasingly deprive them of their usual prey, seals.