LISBON, Portugal (AP) – Wildfires flared again around Portugal’s third-largest city Wednesday, just hours after firefighters brought them under control after fighting a dozen blazes this week.

More than 540 firefighters supported by 150 firetrucks and seven air tankers were battling blazes in the Coimbra district alone. They also were working in the central and northern districts of Porto, Santarem, Vila Real, Viseu.

Four more people were arrested Wednesday on suspicion of arson – raising to 122 the number of people detained this year on suspicion of deliberately starting fires. Eighty people were arrested last year for arson in Portugal.

Portugal has had little or no rain for 10 months, with at least 75 percent of the country suffering through an extreme drought, the Water Institute said.

After days of fires, a cooling fog and higher humidity helped firefighters bring the flames under control Wednesday before they flared up again, officials said.

The fire has destroyed at least 10 houses in the suburbs of the city of Coimbra, about 120 miles north of Lisbon. About 50 residents were evacuated from villages Tuesday night, officials said.

Some residents were due to return to their homes, Coimbra’s Gov. Henrique Fernandes said, but many will find a blackened landscape.

More than 1,620 firefighters were involved in the effort, and about 600 members of the armed forces were deployed to areas where fires were under control.

Several countries, including Spain, Germany, France and the Netherlands, sent pilots and equipment. Slovakia also said it was prepared to send a helicopter.

In the Miranda do Corvo area of Coimbra, residents applauded as German helicopters helping to fight the blaze flew overhead, dousing flames with water, the Jornal de Noticias newspaper said.

“As soon as they got here, they rolled up their sleeves and set up a communications room,” Portuguese air force pilot Mario Marcao told the newspaper.

Three French firefighters from a special natural disasters unit in Nice, France, cut short vacations to help out.

Women walked long distances to bring drinking water, wine, juice and food to firefighters working days on end. Other residents helped by bringing crews buckets filled with water.

Wildfires have killed 15 people, 11 of them firefighters, this year, burning through 445,000 acres, compared with 320,370 acres last year.

Other parts of southern Europe also were ablaze. In Spain, enduring its driest year since keeping rainfall records in the 1940s, dozens of fires were burning in the northwest Galicia region and other areas.

Fires on the Mediterranean island of Corsica scorched 1,480 acres of brush in July. Separate fires in France’s southern Bouches-du-Rhone region destroyed more than 7,400 acres of brush and pine forest in July. August fires devastated about 1,700 acres of woodland in the Vars and Bouches-du-Rhone regions of southeastern France.