A wildfire is burning north east of Athens, darkening the sky as the smell of smoke and soot pervaded the Greek capital.

More than 400 firefighters, 110 fire engines and a large number of volunteers were fighting the blaze, which broke out around 3pm local time about 22 miles from Athens.

The 15 firefighting planes and nine helicopters were operating by late afternoon, but stopped at sunset.

The flames were moving fast towards Lake Marathon, an important reservoir supplying Athens with water, said fire colonel Vassileios Vathrakogiannis, a spokesman for the fire department.

An unknown number of houses have been damaged.

Greece Wildfires
A firefighter sprays water with a hose in Varnava village during a wildfire (Michael Varaklas/AP)

Mr Vathrakogiannis said winds reached gale force strength in the area of the fire and flames exceeded 80 feet in height.

Residents of the villages near the area of the fire have been warned by emergency text messaging to evacuate.

Late in the afternoon, messages were also sent to residents of some northern Athens suburbs to do the same.

Police said they evacuated more than 200 individuals, mostly elderly and others who did not heed the warnings.

Another fire that broke out to the west of Athens has been contained, the spokesman said.

Hot and dry weather, made worse by strong winds, increases the danger of wildfires. 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 will be under a red alert, climate crisis and civil protection minister Vassilis Kikilias said.