At least 61 people have been killed in several raging forest fires in central Portugal, many of them trapped in their cars as flames swept over a road, officials said Sunday.

Interior Ministry official Jorge Gomes said at least 16 people were killed when their vehicles were engulfed by flames on a road between the towns of Figueiro dos Vinhos and Castanheira de Pera, Sky News reported.

"The smoke cloud is very low, which does not allow helicopters and fire planes to work efficiently, but we're doing everything possible and impossible to put out this fire, " he said.

Nearly 60 other people were injured, including four firefighters and a seriously injured minor, Gomes told state broadcaster RTP.

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 yards ahead. A young man was seen sharing a bottle of water with a distraught woman as she stumbled down the road.

A lightning strike is believed to have sparked the blaze in the Pedrogao Grande area after investigators found a tree that was hit during a "dry thunderstorm," the head of the national judicial police told Portuguese media. Dry thunderstorms are frequent when falling water evaporates before reaching the ground because of high temperatures. Authorities had previously said that 104 F heat in recent days might have played a part in the inferno about 95 miles northeast of Lisbon. About 700 firefighters have been trying to put out the fires since Saturday, Gomes said.

Prime Minister Antonio Costa called the recent fires "the biggest tragedy of human life that we have known in years."

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.

"The priority now is to save those people who could still be in danger," he said Sunday.

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

Portugal's civil protection agency, which coordinates the firefighting efforts, issued a warning of the increased risk for forest fires in Friday. Citing the high temperatures, it said that all outdoor fires were prohibited.

The European Union has activated its civil protection efforts to help Portugal extinguish the fires. EU Commissioner for Humanitarian Aid and Crisis Management Christos Stylianides expressed his condolences for the victims in a statement, saying the "EU is fully ready to help."

Stylianides says that in response to a request for help by Portugal, Spain and France are both sending aircraft to help fight the flames. France is sending three planes, while Spain has sent several firefighting aircraft, including two water-bombing planes, to help fight the fires.

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."

Read more from Sky News.

The Associated Press contributed to this report.