The deceased were travelling in the same helicopter. The two people in the other helicopter, a Greek and a Briton, survived.
"I express my deepest sorrow over the tragic accident involving the two leased firefighting helicopters that cost the lives of two frontline fighters in the war against the fires under very adverse weather conditions - especially for our aviation resources," writes Greek Prime Minister Kyriakos Mitsotakis on X.
Strong winds
The fires are raging outside Athens, among other places, and the helicopter accident occurred in the Psatha area west of the capital. It is there, at the coastal resort of Porto Germeno, that the fire situation has been worst since Friday.
Video footage shared by Greek newspaper Proto Thema shows one helicopter flying into the rotor blades of the other from behind. The hit helicopter can be seen falling to the ground in flames, while the other appears to be able to continue flying.
Strong winds in some of the fire areas are both allowing the fire to spread quickly and making the work of helicopter pilots more risky, as authorities have warned. But whether the winds had anything to do with the accident is unclear.
23 aircraft and helicopters have been deployed to fight the fires across Greece.
Man arrested
Around 500 firefighters are fighting to keep the flames around Porto Germeno from reaching the outskirts of Athens. Around 100 firefighters are trying to put out another fire in Aigialeia in the northern Peloponnese.
A 44-year-old man was arrested on Sunday on suspicion of starting a fire on the island of Kefalonia late Saturday night.
A total of five firefighters have now died in the latest fires. Two firefighters have previously died in Crete and one in the Peloponnese.
Corrected: In a previous version, the wrong day was given for one of the fires.
