Eighteen burned bodies, possibly of migrants, were found on Tuesday in a rural area in northern Greece where wildfires have been burning out of control for a fourth day, the fire brigade said, as gale force winds fanned blazes across the country.

The Evros region in northeastern Greece is a popular route for migrants from the Middle East and Asia crossing the river from Turkey into the European Union. Authorities have reported an uptick in crossings this month.

The bodies were found near a shack south of the village of Avantas, authorities said, near the vast Dadia forest. Another body thought to belong to a migrant was found on Monday in a rural area 40km away.

“Given that there have been no reports of disappearances or missing residents from the surrounding areas, the possibility that these are people who entered the country illegally is being investigated,” the fire brigade said. It said searches were ongoing.

Earlier on Tuesday, dozens of hospital patients, including newborn babies, were evacuated onto a ferry as hundreds of firefighters struggled to contain the blaze that broke out near Alexandroupolis on Saturday.

It spread quickly, fanned by high winds, sending plumes of smoke above the port city and turning the night sky red.

Fires also broke out on Tuesday near the capital Athens, where a blaze on the city’s outskirts, on the foothills of Mount Parnitha, burned homes and forced residents to flee.

Another fire burned uncontrolled in the industrial town of Aspropyrgos. More than 120 firefighters and nine aircraft were fighting the blazes near Athens.Southern Europe has been hit by a new heatwave with temperatures reaching or exceeding 40 degrees Celsius in some parts.

By early Tuesday, authorities said 65 patients at the University Hospital of Alexandroupolis had been evacuated as a precaution onto a ferry in the port.

The ferry was turned into a makeshift hospital. Elderly patients lay on mattresses on the cafeteria floor, paramedics attended to others on stretchers and a woman held a man resting on a sofa, an IV drip attached to his hand.

"I've been working for 27 years, I've never seen anything like this," said nurse Nikos Gioktsidis. "Stretchers everywhere, patients here, IV drips there ... it was like a war, like a bomb had exploded."

The ferry later sailed to the nearby port of Kavala, state broadcaster ERT said.

Fourteen more people were evacuated by a coastguard vessel from a beach near the village of Makri.