At least 57 people have been killed in forest fires in central Portugal, many of them trapped in their cars as flames swept over a road.

Interior Ministry official Jorge Gomes said the deaths occurred in the Pedrogao Grande area, about 93 miles northeast of Lisbon, where some 600 firefighters are trying to put out the fires over the weekend.

Gomes said 16 people were killed in their cars on a road between the towns of Figueiro dos Vinhos and Castanheira de Pera, and three others died from smoke inhalation in Figueiro dos Vinhos.

Public broadcaster RTP said there were about 20 injured, including six firefighters. Fourteen of the injured were in serious condition, RTP said.

Prime Minister Antonio Costa called it "the biggest tragedy of human life that we have known in years." He said Portuguese authorities were working on identifying the victims and that Spanish rescuers would assist in efforts to control the blazes.

Televised images showed a huge wall of bright red flames leaping over the top of trees in the wooded region.

Portugal has suffered high temperatures that have reached 40 degrees Celsius (104 degress Fahrenheit) in recent days.