Forest fires have hit two million hectares (7,700 square miles) of Siberian forest, where global warming has caused an "exceptional drought", environmental Group Greenpeace said Tuesday.

The Russian federal forestries agency confirmed the problem while giving a much lower estimate of the land affected, putting the figure at 125,000 hectares.

Greenpeace Russia spokesman Alexey Yaroshenko told AFP the situation was "an unprecedented catastrophe in Siberia," which he said was due to "the ineffectiveness of the authorities" but, above all, global warming.

The fires peaked last Thursday, around the Siberian cities of Krasnoyarsk and Irkutsk near Lake Baikal where nearly five million people live and some schools had to be closed.

The area was covered by thick smoke, said Yaroshenko.

Since then much-needed rain has shrunk the affected area but "around 900,000 hectares are still on fire today", he added.

On Sunday Russia's minister of emergency situations, Vladimir Puchkov, called for additional measures to protect residents in the affected areas and spoke of "the inability to truly evaluate the area" of the fire-affected regions.

Satellite surveillance remains hampered by the cloud of smoke, he added.

Fires destroy huge areas in Russia each summer, mainly in the eastern region of Siberia, leaving poorly funded government agencies struggling to contain them.

Particularly devastating fires struck in 2010, including around Moscow.