Hot dry weather in Greece -- not unusual for this time of year -- has heightened the risk of summer wildfires, and scientists say human-driven climate change is making them more frequent and more intense.

The new wildfire broke out at Koropi, a town some 30 kilometres (20 miles) east of Athens, where residents received text messages from civil protection units urging them to evacuate the vicinity.

That fire "has reached the courtyards of the houses", Koropi mayor Dimitris Kiousis told public television channel ERT.

"The fire is ongoing. All residents (in threatened areas) have been evacuated," Thodoris Grivas, deputy mayor of Koropi, told ERT.

"We do not yet know the extent of the disaster," Grivas added.

Early on Friday afternoon, at least two water bombers and two helicopters were battling flames fanned by strong winds blowing across Attica, the Athens region, and the capital itself.

The fire was destroying olive trees and brushwood, ERT images showed.

Firefighters earlier managed to bring under control a separate fire which had on Thursday threatened the port of Rafina, around 20 kilometres northeast of Koropi, after some 300 local people were evacuated from their homes.

Fire crews remained on alert, as the Rafina wildfire was not far from Athens International Airport and winds still posed a threat.

The blaze destroyed a several houses and vehicles, local mayor Dimitris Markou told ERT.

It also disrupted ferries to and from tourist islands in the western Aegean, including Mykonos.

- Winds abating -

On the island of Crete, around 230 firefighters, 48 fire engines and six helicopters remained at the scene near the resort town of Ierapetra, even though the blaze was receding.

Some 3,000 visitors had been forced to leave their hotels and guest houses on Wednesday evening and 2,000 local residents were also evacuated, authorities said.

"The fire is retreating," fire department spokesman Vassilios Vathrakoyannis told AFP.

"There are still fears of flare-ups but there is no longer a major front," he added.

Scattered hot spots still remained and firefighters were dealing with several smoke-filled areas from which flare-ups had restarted, the fire department told the ANA press agency.

Weakening winds in the hard-to-reach area had improved the situation, firefighters said, although a fire brigade spokesperson had warned overnight of some "difficult" days ahead.

Greece had until now been generally spared the heatwave roasting parts of Europe, particularly Spain, Portugal and France over recent days.

But starting this weekend, temperatures are forecast to rise, reaching up to 43 degrees Celsius (109 Fahrenheit) in some areas of the country.