Two helicopters deployed to battle wildfires near Athens, Greece collided on Sunday, amid extreme weather conditions with winds reaching 100 kilometres (60 miles) an hour.

Dramatic footage showed one of the helicopters explode and plunge to the ground in flames after an apparent rotor collision. The teams involved were part of an operation to combat the wildfires currently ravaging the Psatha area west of the capital.

A statement released by the fire service said that "search and rescue teams were immediately mobilised to locate and assist the crews." Both aircrafts have since been located, with the crew members of one of the helicopters involved "safe".

A search-and-rescue operation is under way to find those who were on board the second aircraft.

Greece's prime minister Kyriakos Mitsotakis has warned of "extremely difficult" days ahead, as nearly 500 firefighters continue to battle blazes around the popular coastal village of Porto Germeno, 70 kilometres northwest of Athens.

They were attempting to keep the fire from approaching the western outskirts of Athens after it scaled a mountain overnight.

Some 100 firefighters were fighting another blaze in Aigialia in the northern Peloponnese.

A new fire broke out late Saturday on the Ionian Sea island of Cephalonia, Greece's popular holiday destination.

A 44-year-old man was arrested Sunday in Cephalonia on suspicion of deliberately starting the fire, according to the Greek news agency ANA.

The National Observatory's climate tracker meteo.gr said early estimates indicated that over 6,500 hectares (16,000 acres) had been burned in separate fires on the Gulf of Corinth which also swept Porto Germeno.

It added that meteorological conditions remained adverse "mainly due to strong northerly winds, which, however, have partially weakened compared to previous days".