French president Emmanuel Macron has promised to send about a hundred firefighters to Quebec, Canada, to help in the effort to battle hundreds of uncontrolled forest fires that have forced evacuations and sent a blanket of smoky air across the United States' east coast.
Hundreds of forest fires have burned 3.8 million hectares of land and forced 120,000 people from their homes since March, in an unusually early and intense start to Canada's wildfire season.
Fires in Quebec have this week sent smoke billowing over the border to the United States, where more than a dozen states imposed air-quality alerts on Wednesday.
Quebec Premier Francois Legault said about 520 firefighters were battling the fires in the province, with another 150 due to join soon from the army.
He told reporters that the Quebec was able to fight 40 fires at the same time, "but we have 150 fires so we have to make sure that we focus where the problems are the more urgent".
Some 500 more firefighters are expected to arrive in the next few days from the neighboring province of New Brunswick as well from France, the United States, Portugal, Spain, and Mexico.
On Tuesday, French President Emmanuel Macron announced that about a hundred French firefighters would be sent to Canada to work "alongside their Quebec comrades", and fire experts would be sent as well.
"Canadian friends, reinforcements are on their way," he wrote on Twitter.
In neighbouring Ontario, Canada's most populous province, deteriorating air quality has been forecast due to smoke plumes.
Smoke drifting south has filled the skies above New York City and much of the east coast of the US, with the air smelling like burning wood.
The US National Weather Service issued air quality alerts for virtually the entire Atlantic seaboard.
Health officials from states as far south as South Carolina and as far west as Ohio and Kansas warned residents against spending time outdoors, as the fine particles in the atmosphere could cause respiratory problems.
Schools canceled outdoor activities, and airline traffic was slowed due to limited visibility.
Warm and dry conditions are expected to persist for months, setting Canada on track for its worst-ever year of fire destruction.
This unusually early and intense start to the season has already burned some 15 times the ten-year average of land, said Federal Minister of Emergency Preparedness Bill Blair.
"We're seeing more and more of these fires because of climate change. These fires are affecting everyday routines, lives and livelihoods, and our air quality," Canadian Prime Minister Justin Trudeau said on Twitter.