Greece appealed for EU assistance on Friday to battle wildfires raging on the outskirts of Athens and in the southern Peloponnese region that forced the evacuation of several villages.

Prime Minister Alexis Tsipras said he had requested help to fight the fires and announced army and airforce units were being deployed to help douse the flames.

"All firefighting forces, in addition to the army and the airforce, are on alert," Tsipras said, blaming the outbreak on "emergency weather conditions".

"We all need to stay calm," he said.

Greece had asked for four aircraft from Europe, fire department spokesman Nikos Tsongas told a briefing.

Tsipras, fresh from a bruising vote in parliament on Thursday to approve an unpopular EU-IMF debt deal, was expected to reshuffle his government but such plans have now been pushed back, reports said.

Around 300 firemen with over 100 fire engines, a dozen airplanes and six helicopters were trying to hold back the flames on Athens' doorstep and the Peloponnese, the fire department said.

The fire in Athens broke out on brush land on Mount Hymettus around midday, near the northeastern district of Kareas, and later spread to the outskirts of residential areas.

Within a few hours, it had crossed the mountain and was threatening the districts of Ilioupoli and Glyfada close to the Athens coast.

In the afternoon, a new fire front broke out in Malakassa, north of the capital.

Television images showed residents dousing pockets of fire with buckets and garden hoses as local officials said the blaze was started deliberately.

"This is clearly arson, I heard explosive devices go off in the forest," Vassilis Balassopoulos, the mayor of the district of Ilioupoli that borders the mountain, told Vima radio.

A huge grey cloud billowed over the city, and a nunnery and a children's shelter were evacuated.

Earlier in the day, four villages were evacuated in the Peloponnese peninsula, near the town of Monemvassia, where strong winds fanned a raging wildfire, local officials told state agency ANA.

"It's hellish right now, there are hundreds of pockets of fire," Iraklis Trichilis, mayor of the town of Monemvassia, had earlier told Skai television.

The fire department said five homes in the area had been burned down.

"The town is being evacuated, we can only see two metres ahead of us," said a resident of the coastal town of Neapoli, where a health centre and retirement home were also emptied by authorities.

National civil protection chief Tassos Mavropoulos told Skai TV that reinforcements from the entire Peloponnese region had been rushed to the area, where the operation was hampered by the wind and mountainous terrain.

A fire-fighting plane was forced to make an emergency landing near Neapoli but the two pilots escaped with only minor injuries.

Fire department spokesman Tsongas had earlier warned there could be further damage to property.

"The winds are strong and are not expected to weaken. There could be further damage," he said.

A fire also broke out on the island of Evia and was threatening homes, officials told state agency ANA.

Greece is routinely hit by wildfires at this time of year, many started by arsonists, every summer, fanned by high temperatures and strong winds.

The worst recent major blazes, in the Peloponnese and on the island of Evia in 2007, left 77 people dead and ravaged 250,000 hectares.-Reuters