A wildfire has intensified overnight and swept along forests north of Athens for a second day as firefighters managed to contain other blazes south-east and west of the Greek capital.

A blaze raged uncontrolled and burned forest in the area of Dervenochoria about 30 kilometres north of Athens, a fire service official said on Tuesday.

The fire threatened a pig farm, according to Greek media.

Another fire weakened on Tuesday, having first broke out on Monday in the village of Kouvaras, about 27 kilometres south-east of the Greek capital.

Fanned by shifting winds, that fire had quickly spread to the coastal towns of Anavyssos, Lagonisi and Saronida, forcing people to flee their homes.

However, 230 firefighters assisted by 76 fire engines and five helicopters were still operating at different spots in the area, a Greek fire service official said on Tuesday.

“Civil protection forces gave an all-night fight,” Greek Fire Service spokesman Ioannis Artopoios said in a televised briefing, adding crews have been replaced to tame the fire on multiple fronts.

A mayor told Greek television more than 2800 hectares of land was reduced to ashes along a coast where many Athenians have holiday homes.

A thick layer of white smoke was visible from Athens as a third blaze burned near the seaside resort of Loutraki, about 80 kilometres west of the capital.

The Greek meteorological service has warned of a high risk of fire this week, just as the country is recovering from the first major heatwave of the summer.

A second heatwave is forecast for later this week.

Greece still has memories of a wildfire disaster in 2018, when a blaze killed 101 people in the seaside town of Mati, east of Athens.

-Reuters