The plane operated by Ukraine-based airline Meridian was traveling from Nis in Serbia and on to Bangladesh, via Jordan.
The pilot had reportedly requested clearance to make an emergency landing at nearby Kavala airport due to an engine problem but did not manage to reach it. Communication with the plane ceased almost immediately afterward.
The aircraft was already in flames before it crashed, people close to the crash site told local media.
The mayor of the affected community of Pangeo, Filippos Anastasiadis, said that the plane had been carrying "dangerous material," likely ammunition.
Ongoing explosions at the crash site, say officials
It was carrying mines and around 11 metric tons of weapons to Bangladesh, which had bought the arms. Serbia's defense minister Nebojsa Stefanovic said the cargo included illuminating mortar shells and training shells. It had taken off mid-evening local time from Nis.
Stefanovic said the crew, who were all Ukrainian, were all killed.
The plane crashed on farmland close to two villages that are part of the Paggaio municipality.
The fire service said in a statement that it has cordoned off the crash site.
Local officials said 15 firefighters and seven fire engines were initially deployed to the area. Firefighters faced difficulty approaching the site because of the ongoing explosions, officials said.