Firefighting aircraft from several countries are helping Greece tackle devastating forest fires that have killed at least 60 people.
Military helicopters have been used to fight the fires
Large swathes of Greece - from the island of Evia north of Athens to the Peloponnese in the south - have been ravaged by the inferno since Friday.
Greek police have arrested 32 arson suspects, as investigations continue into the origins of the blazes.
A 1m euro (£678,000) reward has been offered to help catch fire-starters.
Dozens of new fires continue to break out, fanned by hot, dry winds.
The BBC's Malcolm Brabant, in Athens, says the police and intelligence services will be keen to discover if there is any link between the suspected arsonists, and whether they are part of an organised scorched earth campaign.
Greece has the feel of a country on a war footing, our correspondent says.
Soldiers are patrolling suburban neighbourhoods trying to catch arsonists in the act and anti-terrorist squads have been questioning some suspects.
Meanwhile, a top Greek prosecutor has ordered an inquiry into whether arson attacks can be considered terrorism, and prosecuted under Greece's anti-terror laws.
Treating arson as a potential act of terrorism would give authorities broader powers of investigation and arrest.
The fires have gutted hundreds of homes, forcing thousands of villagers to flee and blackening hillsides.
Water-bombing aircraft from France, Italy and Canada are in action, with more international aid expected.
Ancient site safe
Ancient Olympia, birthplace of the Olympics, was in danger on Sunday, but firefighters managed to keep it safe.
Culture Minister George Voulgarakis went to Olympia, in the Peloponnese, to oversee the emergency effort.
"All the people, the firefighters, the policemen, the volunteers, they fought with the fire and the museum is as it was."
The BBC's Dominic Hughes on the island of Evia says several massive fires are burning in the thickly wooded hills. On Sunday five bodies were found on the island.
"Over the weekend the sky was grey-brown over Athens and Kifissia, the air full of smoke and the sun - a dim spot," said Gabriella Gosevits, an Athens resident, in an e-mail to the BBC News website.
"There was ash all over the place and the smell of burnt wood was everywhere."
Thousands of Greek firefighters are being supported by 20 water-bombing planes and 19 helicopters. At least 11 countries are helping Greece fight the fires with planes, helicopters and specialist firefighters.
Prime Minister Costas Karamanlis has declared a nationwide state of emergency.
The reward, put up by the Greek government, is for anyone providing information which leads to the arrest of an arsonist.
One theory is that the fires could have been started as a way of getting around Greek law which forbids development on areas designated as forest land.
The head of the conservation charity WWF Greece, Demetris Karavellas, told the BBC's World Today programme that Greece lacked a forest registry, "so in many cases it's not entirely clear what is forest and what is land for construction".
"There is strong pressure for tourism, for more and more development... I hope the public, at least, with the amazing damage that we are going through right now, will really create a lot more political pressure," he said.
At ancient Olympia, flames licked the edges of the original Olympic stadium and scorched the yard of the museum, home to one of Greece's greatest archaeological collections.
Athens itself was shrouded in smoke that obscured the sun as several fires threatened the city's outskirts.
The rapidly advancing fires caught many people unaware. Those who left the decision to flee too late were caught in their houses, cars, or as they stumbled through olive groves.
At least 39 people were reported to have been killed in the worst affected region, around the town of Zaharo in the western Peloponnese, by a fire that broke out on Friday and quickly spread.