French President Emmanuel Macon has called the wildfire that erupted in the sprawling Fontainebleau forest just south of Paris on Sunday a blaze of “exceptional magnitude.”

“To the residents of Seine-et-Marne, I want to express our solidarity. To the firefighters and rescue forces engaged without respite, our profound gratitude. All available resources are being mobilised,” Macron wrote in a post on X.

Officials described the fire as "very virulent" as it raced across 800 hectares and was still spreading with fire crews rushing to contain it.

The spread caused the partial closure of the A6 highway, the country's main north-south artery, officials said early on Monday.

With nightfall, firefighting aircraft had been forced to suspend their operations.