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.

"It has rained for the past three days and we can now breathe a little at least," said the 37-year-old, adding she had never witnessed fires of this magnitude in the region.

- Controlling the damage -

Regional authorities have advised the public to stay indoors as much as possible to avoid air pollution after raised levels of nitrogen dioxide and carbon monoxide were recorded in some districts.

Doctors screened last weekend more than 9,000 adults and 2,500 children in door-to-door checks in smoke-affected areas, with more than 20 residents requiring medical attention because of the fumes.

On Wednesday -- despite fires consuming a further 67 square kilometres in 24 hours -- regional authorities claimed the air quality was acceptable.

Activists say the blazes are also threatening the fragile ecosystem around the lake, which contains some 20 percent of the unfrozen freshwater on the planet.

The Baikal is one of the world's most biodiverse lakes, with 1,340 animal species -- including a unique variety of freshwater seals -- and 570 different kinds of plants, according to UNESCO. The surrounding area is home to a wide range of forest animals, some of which are endangered.

Environmentalists have sounded the alarm over pollution seeping into the lake from nearby Soviet-era factories and as a result of the fires and tourist activity in the area.

"Dark coniferous forests, which in the Siberian taiga contain pine, fir and spruce trees, suffer the most from the fires," forestry specialist Alexander Bryukhanov at World Wildlife Fund (WWF) Russia said last month.

"These types of trees do not have strong bark to protect them from flames and are very slow to recover from fires. The fire most affects average-sized mammals like foxes, lynx, hares, weasels and others."

Emergency situations minister Vladimir Puchkov said in mid-August that fires raging in the region would be extinguished within a few days, but weeks later the forest is still ablaze.

Local forestry authorities have blamed lightning strikes, dry weather, the deliberate burning of dry grass and reckless breaches of fire safety regulations by the public for the destruction. The emergency situations ministry said some 2,500 workers were out battling the flames.

- Slow response -

Wildfires are an annual occurrence in Russia, in part due to the burning of dry grass in the summer. Abnormally hot and dry weather this summer in Siberia and the Far East have left forests tinder-dry.

Grigory Kuksin, head of Greenpeace Russia's firefighting programme, said the lethargic reaction of national and municipal officials to the fires is part of the reason they are still burning.

"Authorities did not react when the fires could still have been extinguished," Kuksin told AFP, pointing out that cuts to federal funding for firefighting made fire safety lax.

"Authorities in Buryatia and the Irkutsk region [on the western shore of Lake Baikal] have repeatedly lowered their figures for the area affected by the fires to demonstrate to the federal government that the situation is under control.

"Both levels of government... could have done something when the fires started one or two months ago."

In 2013, President Vladimir Putin castigated regional authorities for neglecting wildfire prevention, blaming the problems on "short-sighted and ill-conceived decision-making".

"Dogmatism and corruption are thriving in forestry management," he said.

The Russian leader ordered that the sector be revamped, calling for it to regulate stubble burning and increase funding for wildfire prevention. Still, Kuksin said the measures have not been carried through.

"Now all that we can do is wait for rain and protect the public," he said.

Farmers in Russia often burn stubble in fields to promote crop growth, but uncontrolled burning of agricultural land has become a common cause of forest fires.

In April, at least 34 people died in southern Siberia as a result of wildfires, apparently caused by the careless burning of farmland. Hundreds more were left homeless.

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