Southern Europe is in the grip of a deadly heatwave, with temperatures soaring past 40 C, sparking wildfires that have forced thousands to take emergency action in several countries, and triggering alerts for tourism hotspots.

As extreme temperatures gripped France, the nation's weather agency, Meteo-France, activated red alerts, its most serious warning level, across 12 administrative units stretching from Atlantic Ocean coastal areas to Mediterranean Sea regions, reported Agence France Presse.

"Don't be fooled. This isn't normal, 'it's summer'. It's not normal. It's a nightmare," agricultural climatologist Serge Zaka told the French broadcaster BFMTV.

In Montenegro and Albania, firefighters were racing against scorching temperatures and strong winds to contain rapidly spreading blazes, reported Deutsche Welle.

Flames swept dangerously close to residential areas near Podgorica, the capital of Montenegro, while in southern Albania's difficult-to-access terrain, desperate communities called for aerial assistance.

In Croatia, a team of 150 firefighters worked through the night to protect residential areas from advancing flames near the coastal city of Split. Hungary reported record-breaking temperatures and fires burned along Bulgaria's southern borders.

In Italy, a massive wildfire has been raging for several days on Mount Vesuvius, near Naples, with authorities suspecting arson as the cause. More than 150 firefighters, supported by aircraft and helicopters, are battling the blaze, reported The Times newspaper.

Raffaele De Luca, president of Vesuvius National Park, said: "One can't exclude the hand of man being behind these fires simply because statistics tell us that 90 percent of fires are caused deliberately or through negligence."