In recent years, wildfires have ripped across Russia's vast territory at an unprecedented scale that experts blame on climate change, negligence and underfunded forestry management services.

The head of Yakutia -- Russia's largest and coldest region that has been hard-hit by wildfires this year -- said Thursday that the day off would apply to the regional capital Yakutsk and several other districts.

"Smoke from the fires has an extremely negative effect on people's well-being," Aisen Nikolayev said, in remarks carried by the RIA Novosti news agency.

"In order to minimise these consequences, today I signed a decree declaring tomorrow a non-working day for 11 municipalities," he added.

Nikolayev recommended that residents spend the day at home.

Yakutsk airport was experiencing delays on Thursday with flights being cancelled or postponed due to poor visibility caused by the smoke.

Earlier this week, President Vladimir Putin ordered reinforcements to fight the Siberian fires and sent the head of the emergencies ministry to Yakutia to oversee the operations there.

In the vast and sparsely populated region, blazes have so far burned through more than 9.2 million hectares (22.7 million acres) -- an area the size of Portugal -- according to Russia's forestry agency.

During a visit to Yakutia last month, local firefighters told AFP that they lacked the people, equipment and resources to deal with the scale of the wildfires.

Critics point to a 2015 law that allows regions to ignore blazes if the cost of fighting fires outweighs the expected damages, saying it provides cover for authorities to avoid fighting wildfires.

US space agency NASA over the weekend said its satellite images showed wildfire smoke from Yakutia travelling to the North Pole, calling it a first in history.