Hundreds of people across the country have evacuated their homes since fires erupted in northern Greece on Saturday, fanned by high winds in the summer's second major outbreak.
The fire brigade said several fires were afflicting mainland Greece.
"Conditions remain difficult, and in several cases extreme," Fire Brigade spokesman Ioanis Artopios said.
"All Civil Protection forces remain on alert and are fighting the fires."
He said 202 firefighters backed by volunteers, alongside 65 vehicles and 15 aircraft, some sent from Sweden and Germany, battled the blaze about 20 kilometres north of Athens, near the village of Fyli on the foothills of Mount Parnitha.
The capital has been smothered in smoke and ash since the blaze ignited on Tuesday.
By Wednesday, the flames had spread towards the town of Menidi, where about 150 people were evacuated by bus from three nursing homes to hotels or other care facilities.
"We kept the fire away from homes," Stathis Topalidis, deputy mayor of Menidi, told state broadcaster ERT, describing the evacuation.
"Unfortunately the wind isn't helping at all."
The fire has left a trail of destruction, burning homes and cars in Fyli and forcing residents to flee on foot, some covering their faces with their clothes because of the smoke.
Volunteers loaded sheep in the trunks of cars to save them.
Rescuers discovered 18 burned bodies on Tuesday, believed to be migrants, in an area near Dadia forest in Greece's northern Evros region bordering Turkey, a common route for people from the Middle East and Asia trying to enter the European Union.
In the Greek port city of Alexandroupolis nearby, dozens of hospital patients, some on stretchers, others with IV drips attached to their hands, were evacuated onto a ferry.
A satellite image broadcast on state television showed smoke from the Evros fires had drifted across the country to the Ionian islands in the northwest, not far from Italy.
Summer wildfires are common in Greece but this year they have been made worse by unusually hot, dry and windy weather which scientists link to climate change.
In July, tens of thousands of foreign tourists were evacuated from the island of Rhodes, where a fire burned for a week, burning hotels and resorts as well as swathes of land.
