A key motorway between Athens and the western Greek port city of Patras was closed as a fire blazed nearby on Friday.
Dense clouds of brown-grey smoke drifted across the road near the village of Nea Peramos, about 30 kilometres west of the capital, state television showed.
The fire brigade called on residents of the region and drivers on the motorway by text message to avoid the dangerous spot.
Traffic was diverted to secondary roads, state television reported.
Three helicopters and two firefighting planes dropped water on the blaze, according to the fire brigade.
However, one firefighting aircraft had to ditch due to engine failure.
The pilots were taken to safety, according to state television.
Due to drought and strong winds, the risk of fire was very high, especially in southern Greece.
This would remain the case for the next few days, the Meteorological Office and others warned on Friday.