Two dozen water bombers and helicopters backed by more than 100 firefighters on Tuesday battled a fierce fire threatening one of central Greece's largest olive groves, the fire service said.

The wildfire approaching the Amfissa olive grove has already destroyed 300 hectares (740 acres) of farmland and 900 hectares of brush, fire service spokesman Yannis Artopios told reporters.

Scientists have warned that extreme weather and fierce fires will become increasingly common due to man-made global warming, and Greece's conservative prime minister has linked blazes in the country to climate change. 

Located at the foot of Mount Parnassus and stretching as far as the Gulf of Corinth, the grove in Amfissa, a town 280 kilometres north of Athens, contains hundreds of thousands of olive trees, many of them over 100 years old.

The fire started on Monday afternoon near the village of Sernikaki, 15 kilometres from the ancient archaeological site of Delphi.

An investigation has been launched into the cause of the blaze, which has not reached the 4th-century BC world heritage site, the authorities said.

Fanned by winds of up to 70 kilometres per hour, the flames spread rapidly towards Amfissa.

The Civil Protection authorities warned at the weekend that high winds and temperatures of up to 35 degrees Celsius meant the fire risk this week was "very high" in some regions.

On Tuesday afternoon, 130 firefighters, five water bombers and six helicopters were deployed to combat flames consuming a pine forest near the seaside resort of Porto Germeno, west of Athens.

In the western Peloponnese, a fire that started in Ilia on Sunday was still burning on Tuesday.

In the east of the same region, a blaze near the village of Kranidi led to the evacuation of a hotel on Monday.

Last summer, heatwaves triggered some of the worst wildfires in Greek history, particularly on Evia, the country's second-largest island.

A total of 103,000 hectares were destroyed and three people died.

The Greek government has called for firefighters to be deployed under a European civil protection scheme to bolster its capacity to battle wildfires.

A total of 250 firefighters from nations including France, Germany, Bulgaria, Romania, Finland and Norway have been taking part in the scheme since July 1.