A firefighter operates during a wildfire near the northeastern town of Alexandroupolis, Greece, on Sunday. AP

Greek firefighters backed by water bombing planes battled a fresh blaze on Monday and warned of an "extreme" risk of fires in the region around the capital, Athens.

A large wildfire broke out in the central region of Boeotia, about 100 kilometres (62 miles) north of Athens, rescue services said.

People on a beach and in two communities near where the fire started on Monday were told to evacuate.

Around 56 firefighters assisted by four water-dropping aircraft were battling the flames, an official from the fire service told the media.

Civil protection authorities warned of an "extreme" fire risk in the region around Athens and other parts of southern Greece.

Fires also continued to burn out of control for a third day in northeastern Greece near the port city of Alexandroupolis.

Firefighting crews are deployed on several fronts and are trying to halt the fire's progression towards the Dadia National Park, which suffered substantial damage from wildfires last year.

People watch the flames during a wildfire near the northeastern town of Alexandroupolis, Greece, on Sunday. AP

More than 200 firefighters with the help of aircraft, volunteers and police were battling the blaze.

Seven firefighters and one volunteer had to be taken to hospital with injuries, the official said.

Some 12 communities have been evacuated over the weekend and civil protection authorities urged residents to remain indoors due to the smoke.

The area has been officially declared to be in a state of emergency.

The very hot and dry conditions which increase the fire risk will persist until Friday, according to meteorologists.

Last month, around 20,000 people, mostly tourists, had to be evacuated from Rhodes island after a fire broke out and was fanned by strong winds.

Almost 17,770 hectares (more than 43,000 acres) were ravaged in 10 days in the south of the holiday island in the southeastern Aegean Sea.

At the end of July, Greece experienced its worst heatwave ever for a month of July, with temperatures of over 40 degrees Celsius (more than 104 Fahrenheit) in many places, according to the National Observatory in Athens.

Agence France-Presse