Portugal has declared three days of national mourning after 61 people were killed in raging forest fires.
Many of those killed died while trapped in their cars as huge flames swept over a road amid intense fires Prime Minister Antonio Costa described as the "the biggest tragedy" the country has experienced in years.
A lightning strike is believed to have sparked the initial blaze in the Pedrogao Grande area after investigators found a tree that was hit during a "dry thunderstorm".
Such storms are frequent when falling water evaporates before reaching the ground because of high temperatures.
Authorities had previously said that temperatures which have soared to 40C in recent days might have played a part in the inferno, centred about 95 miles north-east of the capital Lisbon.
Interior Ministry official Jorge Gomes said 59 people died from the flames and suffocating smoke, while another two people perished in a traffic accident related to the fires.
Another 54 people have been injured, including four firefighters and a child with serious injuries.
More than 350 soldiers have joined the 700 firefighters who have been struggling to put out the flames since Saturday.
A huge wall of thick smoke and bright red flames could at one point be seen towering over the top of trees near houses in the wooded region.
Local television showed terrifying images of several people on a road trying to escape the intense smoke that had reduced visibility to just a few metres.
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.
He added that firefighting crews are having difficulties battling the flames, which are "very violent" in at least two of the four fronts.
A Spanish firefighting aircraft is assisting and another is expected to arrive later on Sunday, while France is also sending three aircraft.
In a tweet on Sunday, Mr Costa sent his "deepest regret for the victims... and a word of encouragement and strength for all who help combat this scourge".
The loss of life due to a forest fire is the biggest in memory in Portugal. It has been over 50 years since 25 Portuguese soldiers perished fighting wildfires in 1966.
"We are most likely facing the biggest tragedy of human life that we have known," Mr Costa added.
Valdemar Alves, mayor of Pedrogao Grande, said: "This is a region that has had fires because of its forests, but we cannot remember a tragedy of these proportions.
"I am completely stunned by the number of deaths."
Many world leaders, including French President Emmanuel Macron, Pope Francis and Indian Prime Minister Narendra Modi, have expressed solidarity with Portugal.
Spanish Prime Minister Mariano Rajoy tweeted that he is "overwhelmed by the tragedy at Pedrogao Grande. The Portuguese people can count on our solidarity, support and care".
Sobrecogido por la tragedia de Pedrógão Grande. El pueblo portugués cuenta con nuestra solidaridad, apoyo y cariño, @antoniocostapm. MR— Mariano Rajoy Brey (@marianorajoy) June 18, 2017