He said that "it was not possible to do more than what has been done" in prevention and responding to the fire. "The priority now is to save those people who could still be in danger".
Almost 600 firefighters and 160 vehicles were dispatched late on June 17 to tackle the blaze, which broke out in the afternoon in the municipality of Pedrogao Grande, about 50 kilometers from Coimbra, before spreading fast across several fronts.
So far, no one has been reported killed by the fire inside a house.
Another 54 people have been injured and taken to hospitals, including four in serious condition.
Portugal was sweltering under a severe heatwave over the weekend, with temperatures topping 40 degrees Celsius (104 degrees Fahrenheit) in several regions.
The Portuguese government has declared the state of emergency in the fire area, and also a three-day national mourning from Sunday and Tuesday.
More than 350 soldiers on Sunday joined the 700 firefighters who have been struggling to put out the blaze, schools in the area were closed until further notice and outdoor fires were banned.
The loss of life due to a forest fire was the biggest in memory in Portugal.
European Commission President Jean-Claude Juncker sent a letter to Portuguese President Marcelo Rebelo de Sousa, expressing "profound sadness" for the fire in Pedrogao Grande and offering "most felt solidarity".
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The monthly core CPI was restrained by decreases in the prices of apparel, airline fares, communication and medical care services. The so-called core CPI, which strips out food and energy costs, rose 0.1 per cent in May after a similar gain in April.
We have had large-scale fires before over the past couple of decades - this year is not unusual in that respect - but it is certainly unusual to have so many fatalities in one place.
Hundreds of firefighters were still battling the flames on Sunday.
Costa tweeted his "deepest regret for the victims. and a word of encouragement and strength for all who help combat this scourge". "I commend the bravery of the firefighters". France was also sending three aircraft.
Francis referred to the "devastating fire" at the end of his Sunday prayer, delivered from his studio window overlooking St. Peter's Square.
Spain has sent two water-bombing planes to help their neighbour fight the fires. The European Union said it would provide firefighting aircraft.
Mariano Rajoy has tweeted that he is "overwhelmed by the tragedy at Pedrogao Grande. The Portuguese people can count on our solidarity, support and care".
He added that Portuguese authorities were working on identifying the victims and that Spanish rescuers would assist in efforts to control the blazes.
A raging forest fire in central Portugal killed 62 people, many of whom were trapped in their cars as flames swept across a road in the country's worst tragedy in living memory.
But various local residents said they had been left to their own devices and had seen no firefighters for hours while their homes burned.
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