Fire department spokeswoman Stavroula Malliri said that 156 adults and 16 children have been taken to hospital with injuries. Eleven of the adults are in a serious condition.
Ms Malliri said that strong winds have fanned the flames, with the fires spreading rapidly into inhabited areas, preventing people who are in their homes or in their cars from managing to flee.
Greece has requested firefighting help from the European Union, and Ms Malliri said a military transport plane is arriving with 60 firefighters from Cyprus, while two water-dropping planes are expected from Spain.
Ministers earlier said more than 700 people had been rescued by sea by the coast guard as the fires on either side of Athens left lines of cars torched, charred farms and forests, and sent hundreds of people racing to beaches to be evacuated by navy vessels, yachts and fishing boats.
Winds reached 50mph as authorities deployed the country’s entire fleet of water-dropping planes and helicopters to give holidaymakers time to escape.
Military drones remained in the air in the high winds to help officials direct more than 600 firefighters below.
“We were unlucky. The wind changed and it came at us with such force that it razed the coastal area in minutes,” said Evangelos Bournous, mayor of the port town of Rafina, a sleepy mainland port that serves Greek holiday islands.
The dock area became a makeshift hospital as paramedics checked survivors when they came off coast guard vessels and private boats.
The operation continued through the night.
The fire posed no immediate threat to Greece’s famed ancient monuments, but as it raged inland children’s summer camps and holiday homes were hastily abandoned.
Fleeing drivers clogged highways into Athens, hampering the firefighting effort.
It has been the deadliest fire season to hit Greece in more than a decade.
More than 60 people were killed in 2007 when huge fires swept across the southern Peloponnese region.
“It’s a difficult night for Greece,” Prime Minister Alexis Tsipras said after flying back to Athens from a trip to Bosnia that was cut short.
Greek Fire Service officials issued public pleas for residents in fire-affected areas to comply with evacuation orders and not stay on in an effort trying to save their homes.
Rafina’s mayor said he believed about 100 houses in that area had burned. The fire service was not able to confirm the figure.
Showers that passed over the Greek capital Monday missed the two big fires - one at Rafina, 18 miles to the east, and the other at Kineta, 35 miles to the west.
Heavy rain is forecast across southern Greece on Wednesday.