A state of emergency has been declared in regions of the densely-forested island east of Athens after the blaze broke out, fanned by strong winds and high temperatures.
Water-dropping planes and helicopters resumed flights at first light Wednesday over a major wildfire burning through a protected nature reserve on the Greek island of Evia, where hundreds of people had been evacuated from four villages and a monastery.
The fire that broke out in the early hours of Tuesday on Greece's second-largest island prompted the evacuation of the villages of Kontodespoti, Makrymalli, Stavros and Platana, and threatened the town of Psachna during the night, officials said.
The aircraft were concentrating on areas where access to the dense pine forest was difficult by land.
Over 200 firefighters were in action backed by 75 fire trucks, nine water-bombing helicopters and seven planes along a 12-kilometre front, managing to avert damage to inhabited areas. One volunteer firefighter was hospitalised after suffering burns.
An Italian water bomber was expected to join the fray later in the day after Greece requested EU assistance. A second Italian plane and two more from Spain were due to arrive by the evening.
The flames were fanned by strong winds, hampering efforts to control their spread and carrying smoke from the fire as far as the Greek capital, where the smell of burning wood lingered until late into Tuesday night.
Evia is the second-largest Greek island after Crete and the nature reserve is part of the European Union's Natura 2000 network of protected areas.
"It's a huge ecological disaster in a unique, untouched pine forest," said acting regional governor Costas Bakoyannis.
It's fortunate that we do not have human victims," Thanassis Karakatzas, a deputy regional civil protection officer, told state agency ANA.
Milder winds are predicted for Wednesday, and the fire department said the situation appeared much improved from the previous day although the fire had still not been brought under control.
"We tried with every means we had to control the fire and for it not to enter the village and burn the houses," said Vasilis Pirgos, a villager from Kontodespoti, one of the four villages evacuated Tuesday.
"Thankfully we had support from the air. We had many helicopters over the village dropping water continuously and we managed to save the houses."
A state of emergency was declared Tuesday for the area affected by the fire and the area faced power outages and water cuts on Wednesday, residents said.
Europe's commissioner for humanitarian aid and crisis management, Christos Stylianides, speaking after meeting with Greek Prime Minister Kyriakos Mitsotakis in Athens on Wednesday, said the first Italian plane had arrived and the second was on its way. Mitsotakis later headed to the area of the fire to meet with firefighters.
Michalis Chrisochoidis, Greece's citizens' protection minister, said authorities had "managed to protect people's lives, for there to not be any human life lost, and to save the people's properties."
Spate of fires
Forest fires are common in Greece during the hot, dry summer months.
Greece has been hit by a spate of wildfires since the weekend, fanned by gale-force winds and temperatures of 40 degrees Celsius.
Authorities have repeatedly warned the public not to engage in outdoor activities that could cause fires, such as welding work, burning weeds or lighting campfires and barbecues. Parks and forest areas are closed to the public at times of high fire risk.
Last year, more than 100 people died when a fast-moving forest fire broke out in a seaside area northeast of Athens and raged through a nearby settlement of mainly holiday homes. The fire trapped people in their cars as they attempted to flee, while many other victims drowned as they tried to swim away from beaches overcome by heat and choking smoke.