At least 150 houses were destroyed by a violent blaze that had surrounded a monastery and a dozen villages on the Greek island of Evia on Wednesday, firefighters and a local official said.

The wildfire is just one of some 40 blazes tearing through parts of Greece as a heatwave hits the country.

Three monks from Saint David Monastery on Evia had refused to leave, firefighters on the island said, adding that everyone else had been evacuated from the villages nearby.

"The flames are 30 to 40 metres high and surrounding the monastery. We're suffocating due to the smoke," one of the monks told the ANA Greek news agency by phone.

Argyris Liaskos, the deputy mayor of a nearby village, told Skai television that no aircraft "were deployed to extinguish the fire."

"At least 150 houses burnt," he said.

Evia island is off the Attica peninsula which also encompasses the Greek capital Athens.

A blaze also started near Olympia, the birthplace of the modern Olympic Games, but the ancient site is not under threat, firefighters said.

Around 100 firefighters are battling the flames there, aided by three helicopters and two water-dropping planes.