In the southwestern city of Bordeaux, the mercury reached 41.6 degrees Celsius at around 4:00 pm (1400 GMT), compared with a previous record of 41.2C on July 23, 2019.

All-time records were also broken at meteorological stations in Bergerac, Cognac and Saint Girons, according to the national weather service, Meteo France.

"The maximum temperatures could rise further," Patrick Galois, a forecaster at Meteo France, told reporters.

A temperature of 41C was recorded in the cities of Toulouse and Carcassonne.

The heatwave, the country's second this summer, began on Friday and was forecast to last at least until the weekend.

Galois said the heatwave could last until August 19 or 20.

On Monday, 12 French departments were placed on red alert, the country's highest heat warning, and the national weather service said it was placing four more departments on red alert from midday Tuesday.

More than 60 departments including the Ile-de-France region that includes Paris will be placed on orange heatwave alert, the second-highest.

"The high temperatures are moving towards the north-east and especially the centre-east," the weather service said.

The red alert corresponds to an "extreme heatwave, exceptional in its duration, intensity and geographical extent", with a significant impact on health and human activities.

The French public health agency called for vigilance, urging people to stay hydrated and avoid alcohol and coffee.

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