More than 70 wildfires have started across Greece over the last 24 hours - the worst blazes on the mainland since 2007, officials say.
Fire crews - backed by helicopters and water-bombers - are trying to prevent the flames from spreading to a northern suburb of the Greek capital, Athens.
A state of emergency has been declared in the area, but no casualties have been reported.
The fires have reached the towns of Grammatiko and Varnavas, near Marathon.
A number of homes have been destroyed and thousands of hectares of forest and farmland burnt.
In 2007, wildfires on the mainland killed 70 people and incinerated 6% of Greece's tree cover.
Olive groves torched
The fires broke out late Friday and developed overnight, fed by gale-force winds that kept shifting direction, fire officials said.
Firefighters are now trying to prevent the blazes from spreading to Pendeli, a northern suburb with a panoramic view of Athens.
Much of Pendeli mountain was destroyed in 2007, and futher erosion of the treeline would be an ecological disaster, the BBC's Malcolm Brabant in Athens says.
The flames are also threatening the town of Marathon, one of the landmarks of ancient Greek history.
Olive groves and forests in the hills outside the town, north-east of Athens, have already been torched.
Fire fighting authorities have urged people to evacuate their homes, but many residents have stayed to defend them.
Priests with hoses have joined in the losing struggle, our correspondent says.
The Greek army was forced to move ordnance from one base in the path of the flames. Television pictures showed an army lorry gingerly towing four air defence missiles down a hillside past a wildfire.
The onset of darkness made flying impossible and that is when its feared the flames will pick up, our correspondent says.
"This is a difficult fire because it is a mixed area with homes and forest, meaning that firefighters are focusing their attention on protecting lives and properties," said fire department spokesman Yiannis Kapakis.
The fires are further contributing to the deforestation of the mountains around Athens. Three of the four mountains surrounding the capital have already been stripped of their trees by fire, says our correspondent.
Other fires are burning on the Ionian island of Zakynthos, which has already been hit by fires this summer.
Dozens of fires burnt through thousands of hectares of land in Spain, France, Greece and Italy in July.
According to the conservation group Greenpeace, heat waves and drier conditions are leading to larger and more uncontrollable forest fires across the Mediterranean.
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