A Greek two-seater F-4 Phantom fighter jet has crashed during an air show at Tanagra airport, near Athens, a Greek Air Force official told Reuters.
Video footage from public broadcaster ERT on Saturday, which first reported the crash, showed a column of black smoke rising a few hundred metres from spectators watching the air show.
Two helicopters were battling the fire on the spot.
The fate of the pilots was not immediately known, and it was unclear whether anyone in the crowd had been injured, the official said.
"A search and rescue operation is under way," the official added.
Loudspeakers at the air base were urging people to leave the area, according to ERT.
The aircraft had just taken off when it suddenly lost altitude and crashed, said a journalist from public broadcaster ERT who was at the scene.
There was an explosion immediately after the crash, which happened before thousands of visitors watching the annual "Athens Flying Week".
Defence Minister Nikos Dendias cancelled a trip to Thessaloniki's International Fair to visit the scene of the accident.
