Two crew on a firefighting helicopter crashed and died on Sunday near the seaside community of Psatha, about 40km from Athens, after a mid-air brush with a second helicopter, whose two crew survived.
More than 400 firefighters and 21 aircraft were deployed near the communities of Kandili and Agia Skepi on Monday as plumes of thick black smoke and red flames engulfed lush pine forests.
Europe has been ravaged by wildfires this northern summer after a period of record-breaking heatwaves and little rain — conditions that scientists say have been exacerbated by a fast-changing climate.
France and Spain have been particularly hard hit, although huge blazes there abated over the weekend, providing some respite.
Greece's fire season had been relatively mild by local standards. Then, last week, three firefighters were killed in two separate incidents in Crete and on the Peloponnese.
Authorities are trying to ascertain the cause of the mid-air helicopter crash, which occurred at low altitude.
The area near Psatha has experienced wildfires before. Locals have complained that, while vegetation has been cleared around houses, more needs to be done to build and maintain fire breaks in the forests.
Preliminary investigation suggests a fire that broke out in the nearby area of Boeotia last week and travelled 25km was caused by sparks from vibrating conductors on a private power line transmitting electricity from wind turbines, the fire brigade said.
An electrical engineer and a contractor have been arrested and are being investigated for arson. Faulty power lines have been the leading cause of major wildfires in Greece in recent years, ahead of arson and negligence.
Dense undergrowth from a relatively wet winter in many western and southern European nations, which was then baked in intense heatwaves in May, June and July, has turned many areas into a tinderbox.
In the Netherlands, fire crews were deployed to contain a wildfire in a nature reserve in the south of the country, and evacuated a nearby camping site.
Italy was bracing for another week of extreme heat while the regional government in the northwestern region of Piedmont declared a regional state of emergency due to the ongoing water shortage and wildfires affecting the region.
Vienna recorded a new record temperature of 40.1C on Monday, beating its previous record of 40C set just six days earlier, the national weather service Geosphere Austria said.
The fast-moving flames destroyed lush forests and caused extensive damage to olive trees just months before harvest, an eagerly anticipated annual ritual in many Greek households.
Days of operations have overstretched a thinly staffed and ageing fire service, the legacy of a hiring freeze during Greece's 2009-2018 debt crisis, Nikos Lavranos, head of the Federation of Unions of Fire Service Employees, said.
"A firefighter who is useful to fellow citizens and society is a rested firefighter, not an exhausted one," he said.
