The fire in the area around Viseu, southeast of Porto in northern Portugal, started on Wednesday and has grown by 2,000 hectares in the past 24 hours alone. Around 12,000 hectares have now been ravaged by fire.
Nine people have been injured, two of them civilians seriously.
Around 1,200 firefighters are trying to bring the fire under control with the help of nearly 400 ground vehicles and 15 aircraft and helicopters. The fire appears to have subsided somewhat on Sunday afternoon.
Spain has sent 120 firefighters and 45 vehicles to reinforce the effort in Portugal. Three firefighting aircraft from Italy and Spain have also arrived.
Spain also has its own concerns to deal with. A wildfire has been burning outside the northeastern city of Girona since Friday. The fire has so far ravaged about 2,200 hectares, according to the EFE news agency.
Eduard Martinez, head of operations at the Catalan rescue service, says that firefighters will likely not get the fire under control on Sunday.
A wildfire is also raging outside Greece's second-largest city, Thessaloniki, where several business buildings and residential buildings have been damaged or destroyed.
Evacuation warnings have been issued for three suburbs and in parts of the city residents are being urged to stay indoors and keep windows and doors closed due to toxic smoke.
Strong winds are making the situation more difficult and around 160 firefighters are fighting the fire with the help of a water-bombing aircraft.
A 76-year-old man has been arrested on suspicion of causing the fire through negligence. Sparks from his vehicle are believed to have ignited vegetation next to a road.
