A volunteer firefighter has been placed under formal investigation in France on suspicion of starting a fire in a forest south of Paris, officials say.

He is one of at least six people questioned over the Fontainebleau fire that has burned more than 2,000 hectares (some 5,000 acres) and led to about 1,000 people being evacuated.

Although the fire has been contained, it has not been fully extinguished. Visiting the area on Thursday, President Emmanuel Macron said there would be no leniency for arsonists.

France - like many other European countries - has been experiencing a series of unusual heatwaves. Macron said there had not seen so many fires in France since World War Two.

Prosecutor Diane Ngomsik told AFP news agency that the volunteer firefighter, 18, had initially confessed to "setting fire to twigs with a lighter and petrol" before retracting it.

BFMTV said a second 18-year old man had also been placed under formal investigation - a stage in French criminal procedure which may lead to formal charges and a subsequent trial.

The Fontainebleau forest blaze partially closed the country's main north-south motorway since it started last Sunday.

President Macron said 10% of the forest had been burned, and hailed the fact that there had been no victims so far.

The forest is home to the Palace and Park of Fontainebleau, a Unesco World Heritage site since 1981.

France has registered nearly 11,000 fires since the beginning of the year.

Climate change is driving up temperatures around the world, and Europe is the fastest warming continent, heating up twice as fast as the global average, according to the Copernicus climate service.

This is causing increased summer heatwaves, greater pressure on Europe's water supply, and more intense wildfires.

The record-breaking temperatures across Europe this summer have led to major wildfires, most notably in Spain where at least 13 people have been killed.

And in the UK, firefighters have been battling to contain a "large-scale" wildfire that has spread across more than two miles (3.5km) of dry land in the Cairngorms National Park in north-east Scotland.