The heatwave sweeping through Europe and likened to “hell” has claimed its first lives as temperatures surpassed 40 degrees Celsius on several parts of the continent.

Three swimmers at beaches in France are thought to have died of “hydrocution” - suffering a cardiac arrest when coming into contact with water due to the temperature difference, according to local reports.

A man aged 70 died after jumping into cool water at Marseillant beach, southern France, According to Midi Libre, he was helped out and remained “very calm” but emergency service then failed to resuscitate him when he lost consciousness. Two other people died in similar circumstances of "thermal shock".

A woman, 62, died at Frontignan beach near Montpellier after “having a malaise and drowning” and a man aged 75 also died at another beach nearby called Carnon.

French firemen warned people to enter the water gradually to accustom the body to temperature changes or risk hydrocution in which blood vessels dilated by the heat contract suddenly, raising the risk of cardiac arrest.