A Canadian-built plane fighting wildfires in Greece crashed on Tuesday, as Greek Prime Minister Kyriakos Mitsotakis warned of tough days ahead, with blazes destroying homes and forcing the evacuation of thousands of tourists from the island of Rhodes.

Two pilots were killed when their Canadair CL-215 plane crashed on the island of Evia, east of Athens, the air force said. It gave their ages as 34 and 27.

Video from state-owed ERT TV showed the bright yellow aircraft releasing its load of water before its wingtip apparently snagged a tree branch. Moments later it disappeared into a deep fold in the ground from which a fireball erupted. The plane had no ejection system.

Mitsotakis cancelled a planned visit to Cyprus for Wednesday, and Greece’s armed forces declared three days of mourning. “They offered their lives to save lives,” Mitsotakis said of the pilots. “They proved how hazardous their daily missions in extinguishing fires are … In their memory, we continue the war against the destructive forces of nature.”

ERT separately reported that the body of a 41-year-old stockbreeder who had been missing since Sunday was found burned in a shack in a hard-to-reach area on Evia.

It was unclear whether he had been killed by the fire or had died of other causes before it broke out.

‘What the entire planet is facing’ A third successive heat wave in Greece pushed temperatures back above 40 C across parts of the country Tuesday amid a string of evacuations from fires that have raged out of control for days, whipped on by strong winds.

It’s still unclear how they started, although tinder-dry conditions amid the summer heat mean the slightest spark can trigger a blaze that will spread fast if not quickly quenched. Several people have been arrested or fined across Greece in recent days for accidentally starting fires.

Mitsotakis said on Tuesday the next few days would be difficult, with conditions possibly improving after Thursday.

“All of us are standing guard,” he said. “In the face of what the entire planet is facing, especially the Mediterranean, which is a climate change hot spot, there is no magical defence mechanism. If there was, we would have implemented it.”