A string of blazes that broke out over the weekend in the Aveiro region have injured 12 firefighters, including two seriously, and forced around 70 local residents to flee, according to the civil protection authority.

A 28-year-old Brazilian man who worked for a forestry agency died after being caught in the flames as he tried to retrieve tools from a burning area, the Lusa agency quoted police as saying.

And a volunteer firefighter died of an apparent heart attack as he was eating on a break, the interior ministry said on Monday.

EU chief Ursula von der Leyen said on X, formerly Twitter, that four states were already responding after Portugal -- which owns about 30 water bomber planes and helicopters -- called on European countries to send reinforcements.

"We are urgently mobilising eight firefighting planes via our Civil Protection Mechanism to help local first responders. I thank France, Greece, Italy and Spain for their rapid reaction. This is EU solidarity at its best," said von der Leyen.

Around 5,000 firefighters were battling 26 fires on Monday, with the country placed on alert from Saturday to Tuesday evening because of high temperatures and strong winds.

The fires have burned homes and halted traffic on several motorways.

The risk level varied from "very high" to "highest" depending on the region.

"The situation is not out of control, but it is very complex. Today will be a difficult day, and so will tomorrow," said national civil protection commander Andre Fernandes.

Portugal has seen fewer wildfires than usual so far this year.

Some 10,300 hectares (25,500 acres) were lost to the flames by the end of August -- a third of what was destroyed last year, and seven times less than the average over the last decade.

Lisbon has upped fire prevention funding ten-fold and doubled the budget to fight wildfires since deadly blazes in 2017 claimed hundreds of lives.

Scientists say human-caused fossil fuel emissions are increasing the length, frequency and intensity of global heatwaves, raising the risk of wildfires.

The Iberian peninsula is particularly vulnerable to global warming, with heatwaves and drought exposing the region to blazes.