Large numbers of hungry, aggressive bears are approaching humans and have killed two people in Russia's far east due to depleting food sources, a forestry worker told AFP Monday.

Authorities on Sakhalin island last week said 83 bears had to be shot dead because they were hostile, a figure that has nearly tripled from last year.

"This has never happened before," a local forestry worker told AFP, asking not to be named because he is not authorised to speak to the press.

"There are not enough fish, berries, nuts," he said, adding that overfishing of local salmon was partly to blame.

"There should not have been any fishing nets installed at all this summer, there is so little fish, but they installed them anyway," he said.

Bears who come out to villages in search of food eat dogs and one recently bit a man's hand.

"At this time of year bears should be balls of fat, but these animals have almost no fat at all," the employee said.

A hunter and fishermen died from bear attacks in September, regional forest ministry official Sergei Prokhorenko told local media.

Animals have also attacked cattle and one family found a bear digging out and eating potatoes on their garden plot in late September, local media said.

The forestry worker said emergency services go to local villages to look for aggressive animals.

He expected the crisis to continue until November when malnourished bears usually freeze to death while others go into hibernation.

Sakhalin Environment Watch, a local non-governmental organisation, has long cautioned that overfishing and poaching are leaving the island's rivers empty of fish.

Last week the group said this year's fishing season is a "record flop" following overfishing in previous years.

Sakhalin is a large forest-covered island off the east coast of Russia that lies north of Japan between the Okhotsk Sea and the Sea of Japan.