Greece is investigating whether organised arson groups are to blame for wildfires which now left at least 20 people dead.

Greece's largest current fire has now been burning for five days just outside the city of Alexandroupolis, near the border with Turkey.

Firefighters searching burnt out areas of the region discovered 18 bodies, believed to be migrants, in a forest on Tuesday.

One other person was found dead in Northern Greece on Monday, while another died in a separate blaze in central Greece.

The country's second major blaze is just northwest of Athens and has burnt through homes between the capital city and Parnitha National Park, a dense area of forest.

In just three days, Greece has seen 209 wildfires break out, a fire department spokesperson said.

"Conditions remain difficult and in many cases extreme," Ioannis Artopios said.

The fires have grown thanks to gale-force wind and hot, dry conditions. While the winds are dying down, authorities have warned that the risk of new fires is still high.

Dozens of villages in the northeast region have been evacuated, as has Alexandroupolis Hospital, with a ferry being transformed into a temporary floating medical facility.

With their own emergency services stretched to the limit, Greece has sought help from other European countries.

Germany, Sweden, Croatia and Cyprus have provided extra water-dropping aircraft while more firefighters and water tanks have been sent by Romania and Czech Republic.

The exact cause of the fires is unclear and Greece's Supreme Court prosecutor Georgia Adilini has launched an investigation into whether organised arson groups were operating in the region.

Greece's climate crisis and civil protection minister Vassilis Kikilias has confirmed the northeastern fires started in several places simultaneously.

Across the border in Turkey, wildfires in the Canakkale province are now in their second day thanks to strong winds.

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More than 1,250 people have been evacuated from nine villages and more than 80 are being treated for the effects of smoke.

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Authorities have stopped boats on the nearby Dardanelles Strait, where water-dropping aircraft are refilling.

Turkey's forestry minister Ibrahim Yumakli has said the country's team of firefighters are being supported by more than 24 fire-dousing planes and helicopters.

Meanwhile, wildfires in Tenerife are nearly under control after ripping through 1,500 hectares (nearly six square miles) in a week, authorities have said.

Italy has also reported fires amid temperatures above 38C (100F) near the popular summer destination of Sanremo.