More than 60 people have been killed since Saturday, when a wild fire broke out in the Pedrogao Grande region some 150 kilometres north of Lisbon, the capital.
The fires began on Saturday during an intense heatwave and rainless thunderstorms, with temperatures of more than 40C (104F) in some areas.
Mr Gomes said at least 30 of those killed were in vehicles engulfed by flames on a road between the towns of Figueiro dos Vinhos and Castanheira de Pera.
Interior Ministry official Jorge Gomes has been quoted as giving the new figure on public broadcaster RTP.
Xavier Viegas, an expert on forest fires, said the blaze spread too quickly and violently for firefighters to respond in some villages, but the deaths have mainly shown shortcomings in communications to evacuate people in time.
Valdemar Alves, the mayor of Pedrogao Grande, said the region "cannot remember a tragedy of these proportions".
Ideally, he said, there should be firebreaks such as cleared woodland or farmland that help to stop a blaze in its tracks.
The loss of life due to a forest fire is the biggest in memory in Portugal. He said 17 others died outside their cars or by the road, 11 people died in the forest, two people died in a auto accident related to the fire and information was missing on the other deaths.
"Those are places I've visited in the past, and to see the images of the roads covered by fire with all those cars, it's really bad", said Silva, who has lived in Toronto for the past 14 years.
Fire and smoke is seen on the IC8 motorway during a forest fire near Pedrogao Grande.
Two more Spanish airplanes and two Italian aircraft will also be deployed, according to the European Commission.
"Winds should not be much of an issue [as Saturday], but that does not mean localized wind issues could occur, especially around the fire", Roys said. "The magnitude of this is on a completely different scale to what I have seen before".
"There are people who arrived saying they didn't want to die in their homes, which were surrounded by flames", said Ansiao resident Ricardo Tristão. "I never thought it would come to this side", she said.
Mr Costa tweeted his "deepest regret for the victims.and a word of encouragement and strength for all who help combat this scourge".
"I am shocked and horrified by the many lives claimed by today's devastating fires", said UN Secretary General Antonio Guterres, who comes from Portugal.
Dozens of terrified civilians fled their homes after the forest fires broke out in Portugal and during their escape, they spoke about the hard scenes.
Spain's prime minister has offered support to Portugal after forest fires have killed at least 43 people in the neighboring country. People, bewildered, remains of homes burning uncontrollably, concrete posts exploding over roads.