NASA has tracked smoke from a multitude of Siberian forest fires that has crossed the Bering Sea to Canada.

The total area of the Siberian blazes increased on Friday to about 31,000 square kilometres, according to Avialessokhrana, Russia's aerial forest protection service.

"The smoke from the Siberian fires can now be seen stretching across eastern Russia, into Alaska, down the west coast of Canada and, then, over Vancouver and Seattle," said Colin Seftor, atmospheric scientist at NASA's Goddard Space Flight Center in Greenbelt, Maryland.

"Smoke from fires burning in the Northwest Territories in Canada can also be seen in the image as well as dust throughout the southwestern US.”

The fires, which have cast a pall of smoke over hundreds of Russian towns and cities, are occurring during dry conditions that aren’t expected to ease soon.

The head of Russia's meteorological service said he saw climate change as a factor behind the wildfires blazing throughout Siberia and the country's far east.

--- With files from The Canadian Press