Authorities declared three days of national mourning as more than 900 firefighters and 280 vehicles battled the blaze, which also left 62 people injured, amid scenes of devastation.
The fire erupted Saturday in the municipality of Pedrogao Grande in central Portugal, apparently caused by a lightning strike, and spread furiously in several directions.
"The fire has reached a level of human tragedy that we have never seen before," said a visibly moved Prime Minister Antonio Costa, who announced three days of mourning starting on Sunday.
"We will certainly find other victims on the ground" in searches from village to village, added Costa.
"I am shocked and horrified by the many lives claimed by today's devastating fires," said UN Secretary General Antonio Guterres Sunday.
"The United Nations stands ready to assist in any way possible," he added.
The expanse of wooded hills in the area north of Lisbon, which 24 hours before had glowed bright green with eucalyptus plants and pine trees, was gutted by the flames.
A thick layer of white smoke hovered over either side of a motorway for about 20 kilometres (12 miles), as blackened trees leaned listlessly over charred soil.
A burnt-out car sat outside partly destroyed and abandoned houses, while a few metres away police in face masks surrounded the corpse of a man hidden under a white sheet.