LE PORGE, France — Firefighters held a vast wildfire inside its perimeter in southwestern France on Saturday, allowing about 198,000 people to return home after what may have been the country’s largest peacetime evacuation, even as renewed fires forced thousands from their homes elsewhere in France and Greece.

In the Mediterranean Var, a fire thought to have stopped advancing raced across 10 square kilometers (4 square miles) in six hours on Friday — “faster than a horse at full gallop,” the prefecture said.

The opposing movements — mass returns in France’s Gironde region, renewed displacement in the Var and boat evacuations from a Greek resort — underscored how quickly days of firefighting progress can be reversed.

At their peak, fires in France and Spain alone drove some 330,000 people from homes and vacation sites, stretching firefighters, aircraft and emergency services across simultaneous crises.

Europe is Earth’s fastest-warming continent, heating at more than twice the global average since the 1980s, according to the European Union’s Copernicus climate service. Rising temperatures and prolonged drought dry vegetation, allowing fires to spread faster and burn more intensely.

The Gironde fire has burned 420 square kilometers (162 square miles) of pine forest west of Bordeaux, an area four times the size of Paris.

Firefighters said it remained contained within that perimeter Saturday, meaning flames had not broken beyond its existing boundaries. But it had not been declared “fixed” — the point at which crews determine that a fire is no longer advancing — and active sectors and buried hot spots persisted.

Several communities remain largely deserted, however. Authorities kept the affluent, forested Cap Ferret peninsula mostly empty because a nearby hot spot could flare again, threatening its limited road access and trapping residents and tourists.

“Today, the fire is still not fixed. It is contained,” Lt. Col. Eric Pitault told reporters.

Crews used tactical burns overnight, deliberately consuming vegetation ahead of active sectors to deprive the main fire of fuel. They still faced about 240 kilometers (149 miles) of fire edges where heat can remain buried underground and erupt again.

The fire’s toll extended beyond people and property. Allain Bougrain-Dubourg, president of France’s League for the Protection of Birds, told RMC radio that animals affected already numbered in the millions.

In the Var, a fire declared fixed earlier in the week had raced back across the hills within hours on Friday. The blaze, Var Prefect Simon Babre said, “defies understanding.”

The resurgence showed how abruptly apparent gains could disappear: A fire considered “fixed” earlier in the week consumed another 1,250 hectares in a matter of hours.

Defensive lines protecting vulnerable communities held overnight and no additional ground burned, Babre told French media Saturday.

But the fire remained active. About 2,500 people were still unable to return home, and 1,300 firefighters were deployed.

Twenty French departments were under an orange heat warning Saturday, mostly in the east and southeast. Temperatures of 35 to 39 C (95 to 102 F) were forecast around the Mediterranean, while eight departments faced a high forest-fire risk.

In Greece, hundreds of firefighters fought Saturday to protect Porto Germeno, a popular resort on the Gulf of Corinth, as gale-force winds drove flames through the coastal area between Athens and Thebes.

The fire broke out Friday near the neighboring village of Agios Vasileios. About 300 people were evacuated by sea, and authorities issued several further evacuation orders Saturday.

The damage around Porto Germeno was “inconceivable,” Theodore Giannaros, a wildfire meteorologist at the National Observatory of Athens, wrote on Facebook.

Giannaros estimated that 40 to 50 square kilometers (15 to 19 square miles) had been affected, although authorities had not issued an official burned-area figure.

Reinforcements brought the deployment to 420 firefighters, including 20 specialized forest-fire teams, backed by 19 aircraft and 11 helicopters. Local authorities said homes had been destroyed, but a complete count was not immediately available.

Powerful winds continued to whip up the flames and hamper aerial operations. Greece’s fire service said crews fought 73 blazes Friday.

The Athens region and part of nearby Evia were placed at the highest wildfire alert level Saturday, with winds forecast to reach 88 kph (55 mph). Such conditions can prevent aircraft from making water drops.

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Adamson reported from Paris. Elena Becatoros in Athens, Greece, contributed to this report.