Nearly 300 firefighters battled throughout the night to keep the fire contained.

Hundreds of Greek firefighters fought for a second day on Friday to bring a large forest blaze under control, with better weather conditions providing hope the flames could be subdued.

Nearly 300 firefighters battled throughout the night to keep the fire contained on the Geraneia mountain range, some 90 kilometres (55 miles) from Athens.

"Conditions are much better (today)," fire department spokesman Vassilis Vathrakogiannis told Skai TV, adding that emergency services were "hopeful" that the fire could be contained with the contribution of water bombers.

"We are cautiously optimistic that during the day, with weather conditions gradually improving, we will limit the fire," civil protection deputy minister Nikos Hardalias told reporters.

It is estimated that over 40 square kilometres (16 square miles) of pine forest and other land are estimated to have been razed already, he said.

Fifteen aircraft were assisting operations on Friday and gale force winds are expected to abate. Army clearing machinery is supporting efforts, Hardalias said.

The state civil protection agency on Thursday had said hundreds of people had been evacuated from 17 villages and hamlets in the surrounding area, as well as from local monasteries.

Map of Greece locating the area where a forest fire started near the village of Schinos, prompting evacuations.

To indicate the speed of the fire, Hardalias said it had crossed 10.3 kilometres in less than five hours on Thursday.

"The fire got to within five kilometres of Megara" on Thursday, a local resident told Skai, referring to a coastal town around 60 kilometres west of Athens.

"Vineyards, cottages, crops have been burned, it's a total disaster... many of my friends have had their homes burned," he said.

Officials said a number of properties have been destroyed, but declined to give precise figures before the fire was extinguished completely.

The blaze started late on Wednesday in the Corinthian Gulf village of Schinos, apparently by someone burning vegetation in an olive grove, the civil protection agency said.

Smoke from the fire choked Athens on Thursday with ash falling from the sky.

The national observatory in Athens said the smoke had reached the Cycladic islands as far as Ikaria. The health ministry recommended people limit physical activity and close doors and windows.

Officials said a number of properties have been destroyed in the blaze.

Wildfires pose a challenge for Greece every year during the dry summer season, with strong winds and temperatures frequently exceeding 30 degrees Celsius (86 degrees Fahrenheit).

Hardalias on Friday said the Geraneia mountains fire broke relatively early in the season, around a month before Greece has scheduled to have its water bomber fleet at full strength on June 15.

An equivalent fire in mid-May had occurred 20 years earlier on the island of Samos, he said.

In 2018, 102 people died in the coastal resort of Mati, near Athens, in Greece's worst ever fire disaster.