Greenpeace claim authorities underestimate the scale of destruction, amid warnings of lack of resources to fight fires.
Yakutsk, currently hosting the Children of Asia International sports games was forced to halt arrivals and departures.
Huge damage wrought by forest fires is sparked by failure to apply safety laws, complained Yuri Chaika.
Residents complain of 'severe carbon monoxide poisoning' as satellite images show blanket of smoke across eastern Siberia.
Most fires will not be extinguished, with major cities polluted by fumes.
Greenpeace claims up to 300 times more territory in Siberia is ablaze than officially acknowledged.
Pictures show how drivers face deadly threat from summer fire 'hell' as fuel truck went at top speed to avoid killer spark.
Pro-Kremlin eco-groups echo Greenpeace concerns by highlighting burning of forests which do not appear in government reports.
Oilmen forced to stop work after being trapped in 'horseshoe' of burning taiga, as pall of smoke smothers Irkutsk region where state of emergency imposed.
A quarter of all Russian forests, 89% of stocks in Sakha Republic, could be left to burn, even though they are essential to fight global warming.