Although the fires had reportedly retreated from the capital's suburbs and were burning mainly forest land, unpredictable winds meant populated areas were still at risk.
"The constant shift in the wind's direction is rekindling the flames," fire brigade spokesman Giannis Kapakis told Reuters news agency. "We must all remain calm through this night."
Dozens of homes were burnt down and a state of emergency was declared in the Athens area.
Prime Minister Costas Karamanlis said the country was facing "a great ordeal" but praised the emergency services for making "a superhuman effort".
Italy, France and Cyprus have sent aircraft to help the hard-pressed Greek fire crews.
Police with loudspeakers went through Agios Stefanos earlier on Sunday telling residents to head immediately to Athens.
AT THE SCENE
Malcolm Brabant, BBC News, Drafi, Athens
In leafy suburbs like Drafi, barely a tree has been left standing. A once beautiful green valley has been turned into a giant ash bowl. But almost all the expensive houses somehow survived.
We had to leave our modest home just before dawn as fire raced up the hill, but the flames stopped at the back garden wall. Many residents have similar narrow escapes to recount.
But the biggest casualty has been the environment. The loss of so much foliage is going to have an enormous negative impact on air quality in Athens. The wooded hillsides on the outskirts of the capital acted as its lungs and air conditioning units, providing much needed oxygen and cooler air.
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