Wildfires are ravaging southern France and spreading into Spain, forcing more than 300,000 people to flee ahead of further expected heatwaves during the week.

French President Emmanuel Macron is set to hold a crisis cabinet meeting on Monday, while Spain's Prime Minister Pedro Sanchez will visit areas hit by fires in Valencia, in the East of Spain.

The fire, which began in the Southwest of France in Gironde, has burned 42,000 hectares and has forced one of the largest evacuations in France's history, according to French broadcaster France 24 and local news outlets. The wildfires have also affected 77,000 hectares of the Avila and Toledo areas in Western Madrid.

"The situation remains highly unfavorable," France's Interior Minister Laurent Nunez said on X on Saturday, according to a Google translation. "At the start of the night, in Gironde, the fire became extremely virulent and unpredictable again, generating its own wind and spreading erratically toward the Bordeaux metropolitan area. By the end of the night, it had calmed down somewhat."

Since the start of the disaster, 2,500 firefighters, 1,500 military personnel, and nearly 1,200 police have been deployed to bring the fire under control, Nunez said.

In the latest developments, the main government centre for the Bordeaux area known as the Gironde prefecture, said Monday, "the situation remained generally stable during the night from Sunday to Monday, with no major developments to report."

The gigantic fire has been labelled an extremely dangerous and rare "pyrocumulonimbus" — a type of fire cloud which generates its own winds and whirlwinds, making it "erratic and unmanageable," Nicolas Braz, a firefighter Captain, told AFP.