Hospitals raise alert as heatwave slams Europe

French authorities banned public alcohol consumption in Paris and warned hospitals faced "saturation", echoing warnings from health authorities around Europe as it baked in a deadly heatwave on Thursday.

At least 101 million Europeans faced temperatures of over 35C, with scores of people thought to have been killed by the record-breaking heatwave.

French and British health services reported a surge in emergency calls and visits as the merciless heat struck the elderly and the ill.

France and Spain counted the toll from the extreme temperatures, including a three-year-old boy who got trapped in his family's car.

"We are reaching a saturation point in hospital facilities," Paris police prefect Patrice Faure said. "The number of hospitalisations keeps increasing."

In Paris, 25 cardiac arrests were recorded over 24 hours on Wednesday, compared with fewer than 10 usually, Health Minister Stephanie Rist's office said.

At the national level, she said a fourfold increase in emergency room visits for heat-related reasons had been recorded.

London Ambulance Service said the extreme heat on Wednesday had led to the highest number of life-threatening emergency calls in a day.

AFP calculations based on forecasts from the German weather service and 2025 population projections from the European Joint Research Centre indicated that more than 380 million people would face temperatures of over 30C.

The UN's climate chief Simon Stiell said the heatwave -- made worse by buildings and infrastructure unsuited to such temperatures -- "has the fingerprints of the climate crisis all over it".

"Until humanity stops burning colossal amounts of coal, oil and gas, extreme heat will keep getting worse," he added.

At a community cooling centre in West London, Alley, a 45-year-old man with a disability, fanned his face, complaining that outside it was "baking".

Last month when temperatures hit record levels, "I was in hospital because my blood pressure medication stopped working," he said.

"This time around, I've kept more hydrated and I come and I bring my water bottle here."

Three deaths in northern France's Pas-de-Calais region were "likely" caused by the heat while a prosecutor said a three-year-old boy was found dead in a car in the suburbs of Paris, where temperatures topped 40C on Wednesday.

Two other children died in similar circumstances in France this week.

Faure said public alcohol consumption and sales would be banned in the French capital from Friday.

In Spain, where temperature records have been set for June, the MoMo monitoring system of mortality rates said 212 deaths between Sunday and Wednesday could be linked to the heat.

Italian newspaper Corriere della Sera reported five deaths from the heatwave including two farmworkers and a builder.

In Germany, where temperatures were in the high 30s and expected to hit 40C through the weekend, several outdoor events were cancelled.

Rail operator Deutsche Bahn told customers to avoid travel due to a high risk of disruption from wildfires, heavy rain and thunderstorms.

Switzerland set a June record of 38C while the Netherlands issued its first ever red-alert heat warning.

The deputy director of the EU's Copernicus Climate Change Service, Samantha Burgess, said the hot weather was due to a "heat dome" of trapped air from north Africa in a low-lying high-pressure system, preventing cooler air from moving in.

Temperatures hit 36.4C in Yeovilton, southwest England, on Thursday, making it the hottest June day on record, the Met Office weather service said.

At the Kingsley Court Care Home in Hayes, west London, resident Lucine Nazikian said the world needed to take the heat seriously.

"Nature is angry with us because we destroy everything," she said.

Polly Turton, head of climate action at NGO Shade the UK, said the situation was "the new normal. The sleepless nights we're all experiencing, we are going to have to adapt to," she said.

"At the moment, we are not a well-adapted UK by any means."

Temperatures were expected to fall in western Europe from Friday but eastern Europe was on red alert as temperatures climbed into the weekend.