In neighbouring Spain, at least four deaths were reported.
The fatalities in Portugal occurred in densely forested parts of central and northern part of the country after blazes broke out in “exceptional” weather circumstances, Civil Protection Agency spokeswoman Patricia Gaspar said.
The situation was still “critical” because of unseasonably high temperatures, Ms Gaspar said on Monday.
But cooler, wetter weather is approaching, which may give some respite to firefighters tackling the blazes.
In addition to the dead, 51 people have been injured, including 15 in serious condition, Ms Gaspar said.
She also said that an unknown number of people were still missing.
Portugal has been especially hard-hit by wildfires this year, including one that killed 64 people in June.
An independent investigation into those fires found last week that authorities failed to evacuate villages on time.
The fire destroyed about 29,000 hectares.
A prolonged drought and mid-October temperatures of more than 30C (86F) have fuelled the recent spate of blazes.
Across the border in Spain, some 105 fires were reported in the northwestern Galicia region.
Authorities said that four people had died, two of them trapped in a car.
Thousands of people have been evacuated.
Regional president Alberto Nunez Feijoo blamed arsonists for causing most of the blazes.
He said “Galicia is fed up” with being attacked by arsonists who make the most of weather conditions, adding that some purposely tried to cause most damage by targeting urban areas.
Mr Feijoo says 15 of the fires are posing a risk to towns.
He added that 90% of forest fires each year in Galicia are intentional.
He told reporters: “All of Galicia is weeping this morning for our razed hills, but especially for the loss of human lives.”
Many of the fires were close to inhabited areas.
Schools were closed on Monday and at least 20 planes were joining 350 firefighting units in tackling the blazes.
Light rainfall was expected to help extinguish the flames.
Spanish prime minister Mariano Rajoy, who is from Galicia, travelled to the region on Monday to visit an emergency response centre.
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