Greece’s air force confirmed that the pilots were killed in the crash on the island of Evia on Tuesday.
They were named by the Greek defence ministry as 34-year-old Commander Christos Moulas and his co-pilot, 27-year-old Pericles Stefanidis.
It came as authorities continued to evacuate Britons on the fire-ravaged island of Rhodes on Tuesday, with holiday operators cancelling flights and holidays. Civil protection authorities warned that Crete was also at risk of wildfires while a “red alert” fire risk was issued for Majorca, Menorca and Ibiza due to extreme heat.
Temperatures are set to reach 44C in some areas of Greece on Wednesday.
Footage in a state television broadcast showed the low-flying aircraft disappearing into a canyon before a fireball is seen moments later.
State broadcaster ERT said the incident occurred over the town of Karystos on the island near Athens, where a fire has been burning.
It is believed the plane clipped a tree before plunging into the ravine.
The Greek defence ministry declared a three-day period of mourning for the pilots .
Defence Minister Nikos Dendias said they lost their lives “in the line of duty... while attempting to protect the lives and property of citizens, as well as the environment of our country”.
“Our thoughts are with their families and colleagues, to whom we extend our most sincere condolences.”
Repatriation flights from Rhodes landed in the UK overnight and on Tuesday as holidaymakers spoke of their “traumatic” experiences being evacuated from hotels and sleeping in schools, airports and sports centres on the Greek island.
The Foreign Office estimate that as many as 10,000 Britons are in Rhodes and a further 30,000 are due to head there in the next few weeks, according to The Times.
Many travel firms are continuing to operate flights to the island as the Foreign Office has not formally advised Britons against travel.
Housing Secretary Michael Gove said he plans to holiday on the Greek island of Evia, insisting the region is safe to visit.
Thomas Cook said holidaymakers who “choose to do so” continue to arrive in other parts of the island while easyJet said it had only cancelled package holidays to affected areas of the island.
Holiday firm Jet2 said it had cancelled all flights and holidays to Rhodes until Sunday and around 1,000 Britons in affected areas have either flown home or moved to hotels in unaffected parts of the island. A decision on what happens beyond Sunday will be made in the coming days.
Croatia was also battling wildfires on Tuesday night, with a firefighting plane attempting to douse a blaze on a mountainside in Å½upa DubrovaÄka, near Dubrovnik. Almost 100 firefighters were on the scene and several vehicles, according to local media.
In Italy, seven people died following wildfires in Sicily and violent storms in the north.
Palermo airport was closed temporarily after a fire triggered by 47C temperatures. Authorities responded to more than 55 wildfires across the island, according to the Guardian.
Ferocious storms also claimed the lives of four people in the northern mainland province of Lombardy, including a 16-year-old girl.
About 20,000 people had to leave homes and hotels in Rhodes over the weekend as an inferno spread and reached coastal resorts on the island's southeast, after charring land, killing animals and damaging buildings.
Thousands of Britons have been flown back from the island - with many more facing their summer holidays being cancelled.
Greek Prime Minister Kyriakos Mitsotakis has warned of tough days ahead, 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.”
On Rhodes an investigation has been launched into the causes of the fires and the preparedness and response of authorities, state broadcaster ERT said. It said about 10 per cent of the island's land area had burned.
An assessment by scientists published on Tuesday said human-induced climate change has played an “absolutely overwhelming” role in the extreme heatwaves that have swept across North America, southern Europe and China this month.