Greek authorities further reinforced firefighting forces in the country’s north east on Thursday, where a massive blaze in its 13th day has flared up once more.

Authorities have issued alerts to residents in the area to be on standby for possible evacuation.

More than 100 extra firefighters were deployed, bringing the total to 582, backed by a fleet of 10 planes and seven helicopters from nine European countries, the fire department said.

The fire that started August 19 has decimated homes and vast tracts of forest in the Alexandroupolis and Evros region, near Greece’s border with Turkey.

It has been blamed for 20 of 21 wildfire-related deaths in Greece last week.

Several people, including the two-member crew of a firefighting plane, have lost their lives in wildfires so far this year in Greece. Officials held a minute of silence at the start of a parliamentary debate on the fires.

The reasons for the country’s major blazes this year are under investigation by fire department officials and the intelligence services.

Defending his government’s response to the fires, Greek Prime Minister Kyriakos Mitsotakis said climate change and a protracted heat wave followed by very strong winds were largely to blame for the deaths and devastation.

The political opposition criticised the government’s preparations for this year’s wildfire season.

Sokratis Famellos, of the SYRIZA main opposition party, said: “You left the country unprepared and defenceless against this danger.”

Mr Mitsotakis implied that migrants were responsible for sparking the wildfire in north-eastern Greece, though he noted an investigation was still underway.

He said: “The causes of the fire are under investigation. It is almost certain that the causes were man-made. And it is also almost certain that this fire started on routes that are often used by illegal migrants who have entered our country.”

“We don’t know if it was negligence or deliberate,” he added.

The prime minister did not provide any evidence to back up the claim, noting the ongoing investigation, and said he would not make further comments “at this time”.

Greece is one of the preferred entry routes into the European Union for people from the Middle East, Africa and Asia fleeing conflict and poverty.

Those crossing the country’s land border with Turkey often use mountain and forest trails to evade authorities and head west to the main northern city of Thessaloniki.

“If there are guilty people, we will make sure to locate them,” Mr Mitsotakis added.

“But, I repeat, this is the job of authorities and only of authorities. Incidents of vigilantism and self-appointed sheriffs will not be tolerated by this government.”

Last week, three people — two Greeks and one Albanian national — were arrested and charged with a series of crimes for allegedly rounding up 13 migrants and forcing them into a car trailer, accusing them, without any evidence, of setting fires.

For some of the small blazes, deliberate arson has been suspected and several people have been arrested, while there have also been dozens of arrests for negligence causing fires.

Since the Alexandroupolis and Evros fire began, evacuation orders have been issued for thousands of people in villages and from the main hospital in the city of Alexandroupolis, with the vast majority allowed back once the danger had passed.

Overnight, residents of two villages near the border with Turkey and near a wildlife sanctuary were put on alert for potential evacuation as one of the fire fronts flared up.

The blaze, now burning deep in the forest in the Dadia national park, is the largest single wildfire recorded in the European Union since the European Forest Fire Information System started keeping records in 2000.

Greece has been stricken by hundreds of wildfires across the country this summer, with dozens of new blazes breaking out each day.

The vast majority are extinguished quickly before they spread. In the 24 hours between Tuesday and Wednesday evening, firefighters were tackling 81 fires in Greece, including 47 that had broken out within that timeframe, the fire department said.

Seeing its firefighting forces stretched to the limit, Greece called on other European countries for help.

Hundreds of firefighters from Romania, France, Bulgaria, the Czech Republic, Albania, Slovakia and Serbia have helped battle the blazes, along with 12 aircraft from Germany, Sweden, Croatia, Cyprus, the Czech Republic, France and Spain.