Hundreds of firefighters backed by more than two dozen water-dropping planes are battling a major forest fire raging out of control on the northern fringes of the Greek capital Athens.

A children’s hospital and a military hospital were being evacuated early on Monday morning, the fire department said, while evacuation orders were issued for more than a dozen areas, including Marathon and several Athens suburbs.

Authorities in nearby suburbs were opening at least one sports hall and providing rooms in hotels for evacuees.

A helicopter drops water near Varnava village during a wildfire (Michael Varaklas/AP)

Local media reported two firefighters were slightly injured, while several civilians were treated in hospital for smoke inhalation.

The fire sent a blanket of smoke over the centre of the Greek capital, darkening the sky.

It began on Sunday afternoon about 35 kilometres (22 miles) from Athens and was fanned by strong winds that quickly drove it out of control, fuelled by tinder-dry conditions after repeated heatwaves this summer, coming on the heels of a particularly dry winter.

This year’s June and July were the hottest months ever recorded in Greece, which also recorded its warmest winter ever.

Both meteorologists and government officials have warned of the heightened danger of wildfires because of weather conditions from Sunday until Thursday.

Half of the country is under a “red alert” for wildfire hazard, climate crisis and civil protection minister Vassilis Kikilias said.

A firefighter adjusts his helmet in Varnava village, north of Athens, Greece (Michael Varaklas/AP)

At first light on Monday, more than 500 firefighters and 16 teams of firefighters specially trained to combat wildfires were battling the flames, backed by 152 vehicles and large numbers of volunteers.

Twenty-nine water-dropping planes and helicopters were being deployed in two waves.

Authorities said flames at time towered more than 25 metres (80ft) in height.

The fire department appealed to residents to follow evacuation orders issued by civil protection, with authorities noting that some people who had refused to leave their homes later became trapped and required rescuing, endangering the lives of firefighters.

“During the night, the wind remained strong, creating dangerous situations,” said Colonel Vassileios Vathrakogiannis, the fire department’s spokesman.

“Unfortunately their intensity is expected to increase in the coming hours, and in any case citizens of the areas where the fire is developing must follow the directions of authorities.”

Firefighters inspect flames near a road in Varnava village (Michael Varaklas/AP)

Wildfires are frequent in Greece during its hot, dry summers, but authorities have said climate change is fuelling bigger and more frequent blazes.

In 2018, a massive fire swept through the seaside town of Mati, east of Athens, trapping people in their homes and on roads as they tried to flee in their cars.

More than 100 people died, including some who drowned trying to swim away from the flames.

Last year, wildfires in Greece killed more than 20 people, including 18 migrants who became trapped by the flames as they trekked through a forest in northeastern Greece and were caught by a massive fire that burned for more than two weeks.