More than 250 firefighters backed by 12 water-bombing planes and seven helicopters battled the blaze that broke out on Sunday at 3pm and quickly reached the village 35 km north of Athens.
"The village was surrounded in no time, in no time. It's really windy," resident Katerina Fylaktou told Reuters.
"It started from one point and suddenly the whole village was surrounded."
Authorities sent evacuation alerts for five nearby areas. By early evening, thick brown smoke hung over much of Athens and reached the island of Aegina to its south.
Hundreds of wildfires have broken out across Greece this summer, which has recorded its hottest June and July after its warmest winter. Like elsewhere in the Mediterranean, scientists have linked the fires to increasingly hot, dry weather driven by global climate change.
A European Commission report in April said the 2023 wildfire season in the Europe was among the worst this century. Just this month, fires burned amid extreme heat in Spain and the Balkans as well as Greece.
Greek fire brigade spokesperson Vassilis Vathrakogiannis said the Varnava blaze spread due to gale force winds.
Flames as high as 25 metres swallowed up trees and shrubland.
Another blaze in a forested area near the town of Megara, west of Athens, had been contained by Sunday afternoon, the fire brigade said.
Several other regions across Greece were on high alert for fire risk on Sunday and Monday.
"We are expecting a very difficult week," said Kostas Lagouvardos, research director of the Athens Observatory.
"If the Varnava blaze is not contained during the night, we will have a problem tomorrow," he said.
Fire-fighting aircraft cease operations at dusk.
On Saturday, Climate Crisis and Civil Protection Minister Vassilis Kikilias said he had called for emergency measures involving the army, police and volunteers to deal with forest fires until August 15.
"Extremely high temperatures and dangerous weather conditions will prevail," he said.
"Half of Greece will be in the red."
In June and July, above-normal temperatures were registered on 57 out of 61 days, Lagouvardos said. Greece is forecast to record its hottest ever summer.
