More than 250 Portuguese firefighters, supported by four Spanish aircraft, are battling a major wildfire in a remote mountainous area near their border, authorities said on Monday.

The fire, which has been burning since Saturday in the Ponte da Barca area of northern Portugal’s Viana do Castelo district, is spreading on two fronts and proving difficult to control due to strong winds and high temperatures, according to civil protection chief Marco Domingues. One firefighter has sustained minor injuries.

By late Monday morning, firefighters were also supported by 80 vehicles and nearly a dozen aerial units. One of the main priorities, officials said, is preventing the flames from reaching nearby communities.

"This is an extremely complex fire," Domingues told local media, citing challenging weather conditions and difficult terrain.

Large parts of northern and southern Portugal remain under maximum wildfire alert, with the national weather service (IPMA) warning of "very high to extreme" risk levels due to heat and wind. In response to worsening conditions across much of the country, the government has reinforced firefighting efforts, especially in the north and centre, said Carlos Pereira of Portugal’s National Civil Protection Authority.

Portugal faces destructive wildfires each summer – a trend that experts say is intensifying with climate change, which fuels more frequent and severe droughts and heatwaves.