Residents have fled their homes as a fire tore through a mountainous pine forest west of Athens, churning out smoke that turned the sky orange over the Greek capital.
The fire department said five water-dropping planes and two helicopters are battling the blaze in the Geraneia mountains near the seaside settlement of Kineta between Athens and Corinth, along with 30 fire engines and 70 firefighters.
Authorities said strong winds are fanning the flames and hampering firefighting efforts.
Footage from the Greek TV station Skai showed the fire burning inside yards. Some residents were using garden hoses to try and save their properties, while others escaped in cars and on mopeds.
Authorities were sending 17 firefighting vehicles from across Greece to bolster the forces already in the area.
Three settlements in the area are being evacuated, while a near 13-mile section on two major roads linking the Peloponnese with central Greece was shut down to traffic.
It is not immediately clear how the fire started.
High temperatures of up to 40C have been predicted for Greece, and authorities have warned that the risk of forest fires is high.
These blazes are common in Greece during the hot, dry summers.
The worst by far occurred in 2007, when large swathes of southern Greece burned, killing more than 60 people.