Smoke from the fires reached the Pacific port of Vladivostok, nearly blocking out the sun and prompting weather officials to warn children and the elderly off the streets.

Almost all the land affected -- 30,000 hectares -- was located in the Khingan preserve, officials said, adding that rare Japanese and Far Eastern cranes had luckily flown south.

According to data from the environmental group WWF, up to three million hectares (7.5 million acres) of forest have been destroyed over the past 15 years in Russia's Far East region, due to illegal logging and fires.