Greek planes and helicopters on Wednesday stepped up their battle against a wildfire raging for a second day that has forced hundreds of people to flee mountainside suburbs north of Athens.

Nearly 500 firefighters, 120 vehicles, nine planes and 10 helicopters supported by army units sought to prevent the flames from causing further damage in the suburbs of Penteli, Pallini, Anthousa and Gerakas, home to some 90,000 people.

Greece has been so far spared the kind of scorching heatwave that has seen deadly wildfires destroy vast tracts of land in France, Portugal and Spain, but has instead faced gale-force winds.

Experts blame climate change for extreme weather events and warn that worse is yet to come.

Thirty people, including three firefighters, required medical attention for burns and breathing difficulties, the Greek fire department said.

Several buildings have sustained varying degrees of damage, AFP images showed.

"The sky was red... we left without taking anything with us," a Pallini resident who lost his car and shed to the flames told ERT television.

"The civil protection authority was late in alerting us. The fire was scorching our backs, we left in the nick of time. Had we stayed another 30 seconds it would have burned us," he added.

The house next door was completely gutted, the man said.

Eleni Gerasimidou, a popular Greek comedian, was among those whose homes in Pallini were damaged.

"The house is no longer inhabitable...it has sustained massive damage," she told Alpha TV, pointing to the charred upper floor.

The father of Olympic pole vault Katerina Stefanidi, Yiorgos, told Alpha TV he and some neighbours had fought the flames "with spades and dirt" to save his home, without any help from the fire service.

"The fire was racing faster than a car," he said.

Authorities warned residents to stay indoors and keep their windows shut.

With winds racing at over 100 kilometres (62 miles) per hour, smoke from the fire billowed as far as the island of Crete, hundreds of kilometres to the south, satellite imagery showed.

Wildfires on the foot of Mount Penteli north of Athens were fanned by gale-force winds
Wildfires on the foot of Mount Penteli north of Athens were fanned by gale-force winds AFP / Aris Oikonomou

Residents say fires have struck the area three times in the last three decades.

Greek media reported that an 80-year-old man in Anthousa shot himself dead in despair over the fire, which broke out on Tuesday afternoon.

The wildfires around Mount Penteli north of Athens were fanned overnight by strong winds that constantly changed direction.

"There are two active fronts," civil protection official Vassilis Kokkalis told Athens 98.4 radio. "The winds are so strong that the planes are prevented from making targeted water drops," he added.

The fire was threatening businesses on a major Athens highway, he added.

"It's a fire that will be a cause for concern for several days," Kokkalis said.

Residents in several areas, a paediatric hospital and the national observatory at Athens were evacuated as a precautionary measure.

The police said some 600 people had been moved to safety overnight.

"It was insane, we did not know where to flee," an elderly resident of Anthousa told ERT.

"Embers were falling from the sky, I've never seen anything like it," he said.

Greece has set up a crisis cell and firefighters battled 117 wildfires in the country in the last 24 hours.

Another 87 firefighters were battling a blaze in the Peloponnese, a southern peninsula.

A heatwave and wildfires last year destroyed 103,000 hectares (255,000 acres) and claimed three lives in Greece.

The country's worst fire disaster was in 2018 in the coastal suburb of Mati, claiming 102 lives, just a few kilometres from the area affected by Wednesday's blaze.