At least 150 houses were destroyed by a raging fire that surrounded a monastery and a dozen villages on the Greek island of Evia on Wednesday, just one of over 100 blazes burning in the heatwave-hit country.
Firefighters were also battling a blaze near Athens, while flames threatened Olympia, the birthplace of the Olympic Games where the mayor pleaded for back-up.
"We're waging a battle of the titans!" deputy minister for civil protection Nikos Hardalias told a press conference. "The hardest is still to come."
On Evia, huge flames leapt up from the forest, visible from the sea in what firefighters said was a difficult blaze to control on an island of rolling hills with little visibility.
Three monks from Saint David Monastery had refused to leave, firefighters said, adding that everyone else had been evacuated from the villages nearby.
"We're suffocating due to the smoke," one of the monks told the ANA news agency by phone, adding flames some 30 to 40 metres high were surrounding the monastery.
Police told AFP they would force the monks to evacuate if their lives were in danger.
Around 85 people gathered on a beach and were evacuated on five boats.
Some 100 firefighters backed by seven helicopters and water-bombing planes were mobilised to fight the fire, civil protection officers said.
The authorities said three firefighters had been slightly hurt.
But Dimitris Vourdanos, deputy governor of the region, said that "we are completely unable to intervene by air or by land".
"There are two main fronts which are uncontrollable and several other smaller ones," he told the Kathimerini newspaper.
Argyris Liaskos, deputy mayor of the small town of Mantoudi, said at least 150 houses burned amid a lack of resources to fight the inferno.
"No aerial means have been deployed to put out the fire," Liaskos told Ska TV.
Acrid smoke over Athens
According to Hardalias, Greece has faced a total of 118 fires in the last 24 hours as temperatures soared above 40 degrees Celsius.
Evia island is some 200 kilometres away from Athens, where more than 500 firefighters, a dozen water-bombing planes and five helicopters battled another wildfire on the outskirts of the city.
The blaze started on Tuesday in a pine forest at the foot of Mount Parnitha, one of three ranges that surround the Greek capital, sending plumes of dark, acrid smoke over Athens and leaving carcasses of burnt-out houses in its wake.
Around a dozen houses have been destroyed in the flames, and dozens of businesses, bars and holiday accommodation have been severely damaged in the suburb of Varybombi, 30 kilometres northwest of Athens, officials said.
On Wednesday afternoon, the blaze was coming under control, Hardalias said.
Authorities in Athens have recommended residents stay indoors and wear a mask to protect against the ash and smoke.
'Climate threat'
Over in Olympia, around 100 firefighters were battling the blaze, aided by three helicopters and two planes.
Culture Minister Lina Mendoni is due to go there to evaluate the risks to the ancient site.
But Olympia mayor Giorgos Georgopoulos called for back-up on television. "We need more aerial support," he said.
The European Union's crisis management commissioner said it would help, and Cyprus and Sweden were both sending two water-bombing planes to help battle the fires.
Neighbouring Turkey is also suffering its worst fires in at least a decade, claiming the lives of eight people and forcing hundreds to evacuate in southern areas popular with tourists.
Experts have warned that global warming is increasing both the frequency and intensity of such fires.
Hardalias said earlier in the week that "we are no longer talking about climate change but about a climate threat".