Raging wildfires have turned the shores of the world's largest freshwater lake in Siberia into an inferno, threatening the health and livelihood of locals and raising questions about Russia's ability to protect its natural heritage.

Critics have blamed authorities' slow response for allowing the blazes to get out of hand, quadrupling in size on the eastern shore of Lake Baikal in the last month and forcing locals to shelter from the toxic chemicals released into the air.

Formed some 25 million years ago, Lake Baikal is the world's oldest and deepest lake, with unique wildlife and vegetation both in its waters and the surrounding region.

Fires are now raging in nearby forests, especially on its eastern shore in the region of Buryatia, engulfing an area three times the size of land burnt by wildfires in California this year.

On Thursday, 36 separate fires blazed across 1,434 square kilometres (about 555 square miles) of forest and peat bog in the region, the state forestry agency said.

"Everything is burning," Oksana Mukhina, the manager of a 15-room hotel on the eastern shore of Lake Baikal, told AFP this week.