Almost 1,000 people were evacuated in Corsica overnight, mostly tourists staying at campsites, as 2,000 hectares (nearly 5,000 acres) of scrubland was destroyed, although no casualties were reported. The evacuees were put up in schools and other temporary shelters.
A man suspected of starting five fires in Bastia, a town with a population of 40,000 in northeast Corsica, was arrested late Friday, an official said.
On Corsica at Cap Corse, the most northerly point of the Mediterranean island where the fire had spread overnight into Friday, the situation has been stabilised but the blaze remains rampant in the Sisco commune.
But in Portugal firefighters managed to bring two of the major blazes under control in the centre of the country by Saturday afternoon, the civil protection authority announced, while warning that the heatwave could reignite the fires.
Firefighters have stopped the spreading of the flames from the forest fire that raged in the region of Abrantes since Wednesday, authorities said.
But more than 500 firefigters, nearly 200 vehicles and three water-bombing helicopters remain on stand-by should the fires flare up again, they added.
The other huge fire now under control was at Alvaiazere in the central region of Leiria.
Civil protection agency spokeswoman Patricia Gaspar said a record 220 fires had started on Friday alone.
"Despite the relentless fires, the situation is now more stable," said Gaspar in Lisbon.
Emergency workers on Thursday had nearly gained control of wildfires across Portugal's drought-hit central region, but stronger winds fanned flames in several areas.
In the village of Bracal, flames were being blown towards houses as residents grabbed what they could to aid firefighters, an AFP journalist said.
Some residents voiced anger at authorities after a season of repeated wildfires which have stretched resources.
Six villages had been evacuated around Abrantes on Thursday as fire-dousing planes flew sorties over the flames.
The fires come after more than 60 people were killed in June, and more than 200 injured, in a giant blaze at Pedrogao Grande in central Portugal that raged for five days.
After an uncommonly dry winter and spring, almost 79 percent of the Portuguese mainland was enduring extreme or severe drought at the end of July, according to the national weather office.