Dramatic video shows a freight train in Canada surrounded by wildfire flames and workers requesting an emergency rescue as they report being "encased" in fire.

"This could potentially overtake us here, this has gotten a little scary," a crew member says as the train rushes past burning trees near Armstrong, Ontario.

There are more than 100 wildfires burning in the province, with several northwestern communities under threat. Smoke blanketed Toronto, which woke up to hazy skies and some of the worst air quality in the world.

The wildfires have led to concerns smoke will drift into US cities over the next few days - including in New Jersey, where Sunday's World Cup final is due to take place.

Canadian National Rail said in a statement that the workers who were trapped outside Armstrong were all safely rescued, and that operations have been temporarily suspended in the region.

The statement did not add any further details about how the rescue occurred.

There are currently 838 wildfires actively burning across Canada, according to the Canadian Interagency Forest Fire Centre.

Grand Council Chief Linda Debassige said in a statement on Wednesday that the remote Namaygoosisagagun First Nation in northern Ontario was "devastated by an unexpected and fast-moving wildfire" that severely damaged homes and community buildings.

More than a dozen fires are also burning in Minnesota, a US state on the Canadian border, due to extreme heat, dry conditions, and strong winds.