Raging forest fires in central Portugal killed at least 62 people, many of them trapped in their cars as flames swept over a road, in what Prime Minister Antonio Costa on Sunday called "the biggest tragedy of human life that we have known in years."

Interior Ministry official Jorge Gomes said at least 30 people died inside their cars as they tried to flee. He said 17 others died right outside their cars or by the road, 11 people died in the forest and two people died in a car accident related to the fire. He said there was no information on the other two deaths.

"For sure, we are going to find some more victims," Costa said.

Interior Minister Constanca Urbano de Sousa said the death toll had risen to 62 by the end of Sunday. She said the country's judicial police was expecting to complete the identification of the bodies soon in order to release them as early as possible.

Firefighters work to put out a forest fire near Bouca, in central Portugal, on Sunday. (Rafael Marchante/Reuters)

Gomes said firefighting crews were having difficulties battling the fire, which was "very intense" in at least two of its four fronts. He said authorities were worried about strong winds that could help spread the blaze further.

Gomes said 54 people have also been injured, five of them seriously, including four firefighters and a minor.

The fatalities occurred in the Pedrogao Grande area, about 150 kilometres northeast of Lisbon, where about 700 firefighters have been trying to put out the fires since Saturday, Gomes said.

Gomes said many of the victims were killed when their vehicles were engulfed by flames on a road between the towns of Figueiro dos Vinhos and Castanheira de Pera.

Almost 24 hours after the deaths Saturday night, fires were still churning across the forested hillsides of central Portugal. Police and firefighters were searching charred areas of the forest and isolated homes, looking for more bodies.

"It is a time of pain but also ... a time to carry on the fight" against the flames, President Marcelo Rebelo de Sousa told the nation in a televised address Sunday evening after the government declared three days of national mourning.

A huge wall of thick smoke and bright red flames towered over the top of trees near houses in the wooded region.

Owen Martin and his wife decided to flee their home Arrochela on Sunday after watching the fire get closer to their property.

"It was some distance away," he told CBC News via Skype. "But as the day has progressed today things have got progressively worse."

The reality of the situation hadn't sunk in until they started driving away from their home, Martin said.

"It looks apocalyptic," he said. "Driving through now we've seen just forests that were lush that's just like ash."

Martin had moved to the area a few months ago, purchasing his dream property with a small orchard.

Owen Martin and his wife left their home in Arrochela as raging fires spread 4:20

Local resident Isabel Brandao told The Associated Press that she had feared for her life.

"Yesterday we saw the fire but thought it was very far. I never thought it would come to this side," she said. "At 3:30 a.m., my mother-in-law woke me up quickly and we never went to sleep again. We were afraid the fire would reach us."

A burnt house is seen during the deadly forest fire in Portugal. Officials say so far nobody has died in a home. (Miguel Vidal/Reuters)

RTP showed terrifying images of several people on a road trying to escape the intense smoke that had reduced visibility to a question of a few metres. A young man shared a bottle of water with a distraught woman as she stumbled down the road.

Costa said that firefighting crews were having difficulties in approaching the area because the fire was "very intense." He added that Portuguese authorities were working on identifying the victims and that Spanish rescuers would assist in efforts to control the blazes.

High temperatures in recent days

Costa said that while investigations are ongoing to determine the cause of the fire, authorities believe that the high temperatures of 40 C in recent days may have played a part.

"This is a region that has had fires because of its forests, but we cannot remember a tragedy of these proportions," said Valdemar Alves, mayor of Pedrogao Grande. "I am completely stunned by the number of deaths."

Portugal, like most southern European countries, is prone to forest fires in the dry summer months.

Panicked residents flee as raging fire engulfs homes and cars 1:12

The Portuguese government has declared three days of national mourning for the victims.

Portugal's national soccer team is wearing black arm bands and has stood for a moment of silence with the Mexican team in solidarity with the country's forest fire victims. The ceremony took place before the teams' match Sunday at the Confederations Cup tournament in Kazan, Russia.

The European Commission said it is working with EU member states to respond to the call for assistance.

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."

Juncker wrote in the letter, "Our thoughts are with all the victims, their families and all the brave soldiers of peace that in a very difficult terrain and under challenging circumstances continue to fight this terrible fire."