Europe's unprecedented heatwave has claimed its first casualties, with at least three people reportedly dying from suspected heatstroke in Italy and Spain.

It comes as a record-breaking heatwave swept through the continent, with France recording its hottest ever temperature of more than 45C on Friday.

A 17-year-old farm worker in the Spanish town of Andalusia collapsing from heatstroke while harvesting wheat.

The teenager complained of feeling dizzy, and had a swim in a nearby pool, before he collapsed into convulsions.

He was raced to hospital but later died from suspected heatstroke.

Also in Spain, a 93-year-old man collapsed and died in the middle of the street in the city of Valladolid.

Local police said his cause of death was heatstroke.

At least three people have died as Europe swelters through its worst ever heatwave. Photo / Supplied

In Milan, Italy, a 72-year-old homeless man was found dead beside a railway station.

The continent's worst ever heatwave has prompted health officials to urge residents to stay indoors and hydrated at all times.

France recorded its hottest ever temperature of 44.3C, with schools in Paris dousing students with water.

A report by CBS News said nursing homes around France have been equipped with hydration sensors to battle the sweltering heat.

The country's soaring temperatures have broken the previous national record of 44.1C, during the August 2003 heatwave, according to state weather forecaster Meteo-France.

At least four people have also died in Germany in public bathing accidents — these are believed to have been drownings.

In Catalonia, firefighters were battling a forest blaze that is believed to have begun when a pile of manure at a chicken farm spontaneously combusted in the extreme heat.

Meteo-France's Etienne Kapikian said it was "very probable" the record would be beaten again later today as it was still relatively early in the day.

"(The temperature) will continue to climb and, in some places, we could pass 44C," he said.

A girl cools off in the fountain of the Trocadero in Paris. Photo / AP

The centre of Carpentras was almost deserted in the middle of the day, with cafe owners contemplating empty terraces which usually would be packed.

"We have never seen this," one exclaimed.

French Health Minister Agnes Buzyn warned those who were tempted to plunge into cold water, to only do so in designated public bathing areas.

Ms Buzyn warned that four people had drowned in the past week.

On Thursday, Ms Buzyn complained that, despite a barrage of public health warnings on radio, TV and on public transport, some parents were still leaving their children in hot cars and joggers were out exercising in the midday heat.

Also on Thursday, a six-year-old Syrian child was seriously injured in the Saint-Denis neighbourhood north of Paris after being catapulted into the air by water gushing from an open fire hydrant and then crashing to the ground.

In Spain, firefighters continued through the night to battle an out of control forest fire in the northeastern Catalonia region.

Authorities said more than 700 firefighters, eight helicopters and six water-dropping aircraft aimed to slow the fire's progress until nightfall, when cooler temperatures might give them an advantage.

Firefighters look at burned terrain in La Palma d'Ebre, Spain as authorities try to control a major wildfire that began in a pile of chicken manure. Photo / AP

They were hampered by roasting 44C and very low humidity according to David Borrell, head of the Catalan fire department.

Authorities said the fire is the Catalonia region's worst fire in two decades and 20,000 hectares of hilly terrain are at risk. By Friday, an estimated 6000 hectares had burned.

Fire investigators believe the blaze started with the spontaneous combustion of a pile of chicken manure on a livestock farm.

Spain's northeast was on red heatwave alert denoting "extreme risk". The stifling temperatures have caused air quality to nosedive in some European cities, prompting local authorities to take anti-pollution measures.

In Paris, Lyon and Marseilles, authorities have banned the most polluting cars from the roads in recent days.