People cool themselves in a fountain at the square in front of Louvre Musuem in Paris, France, June 28, 2019. (Photo/Xinhua)

PARIS/MADRID - Hundreds of firefighters brought wildfires under control in southern France on Saturday as Europe sweltered on the sixth day of a widespread, deadly heat wave that has fulled record-breaking temperatures, killing at least six people.

In the worst-hit Gard region, where France's highest-ever temperature was registered on Friday at 45.9 C, scores of overnight fires burned about 550 hectares of land and destroyed several houses and vehicles.

"We came very close to a disaster," Didier Lauga, prefect of the Gard, told reporters. "There are still firefighters in place in case fires break out again."

A mentally unstable man was arrested after starting a blaze in one village, but the extreme heat was likely to blame for many of the fires, Lauga said.

Fifteen firefighters and several police officers were injured in the Gard, where 700 firefighters and 10 aircraft were mobilized to contain the flames, emergency services said.

In the neighboring Vaucluse region, authorities said a man who had been cycling in a mountainous area had died after collapsing due to the heat.

It is not only humans struggling in the heat.

Winegrowers in the south of France said their precious crops have been badly burned.

"Some vines seem to have been hit with a blowtorch," Jerome Despey said, while Catherine Bernard likened it to the effects of a hair dryer. "I've been a winegrower for 30 years. I have never seen a vine burned by a sudden onset of heat like yesterday," Despey added.

France is the seventh European country to ever register a 45 C temperature, along with Bulgaria, Portugal, Italy, Spain, Greece and North Macedonia, Meteo France said.

In Germany, organizers of Sunday's Frankfurt Ironman race made contingency plans to keep athletes from overheating in temperatures expected to reach up to 38 C.

The World Meteorological Organization said this week that 2019 was on track to be among the world's hottest years, and 2015-19 would then be the hottest five-year period on record.

It said the European heat wave was "absolutely consistent" with extremes linked to the impact of greenhouse gas emissions.

Temperatures soared in the United Kingdom on Saturday as the island country saw its hottest day of the year. A scorching 34 C was recorded at Heathrow and elsewhere in west London, making it one of the hottest June days for about 40 year, the Met Office said.

The hot spell sparked several blazes, including in Spain where firefighters were again battling high flames in strong winds and blistering heat on Saturday just after they managed to contain another inferno after nearly 72 hours.

A fire that started on Friday in the central Spanish town of Almorox burned at least 1,600 hectares, spilling over into the Madrid region and forcing the evacuation of a village, emergency services said.

At least three people died in central and northern Italy, while hospitals in the financial capital, Milan, saw a 35 percent rise in emergency visits due to heat-related conditions, local media reported.

Demand for power in the city surged as people cranked up air conditioning, leading to sporadic blackouts in stores and restaurants. Temperatures are forecast to ease in the coming days but it will remain hot.