The Black Hawk helicopter landed after sending a distress signal to authorities at the airport in Alexandroupolis in the country’s north.
Seven of those on board were in military uniform and all are believed to have been involved in the attempted putsch, ERT TV said.
Turkey’s Foreign Minister Mevlut Cavusoglu said Ankara had asked Athens to send back the eight coup plotters.
“We have requested Greece to extradite the eight traitors as soon possible,” Cavusoglu was quoted as telling HaberTurk television.
According to an official in the Greek National Defence General Staff, “the helicopter is scheduled to be sent back immediately to Turkey”.
Greek Prime Minister Alexis Tsipras early Saturday expressed his “support for the democratically elected” Turkish government.
What happened in Turkey?
Forces loyal to Turkey’s government fought on Saturday to crush the last remnants of a military coup attempt which collapsed after crowds answered President Tayyip Erdogan’s call to take to the streets and dozens of rebels abandoned their tanks.
More than 160 people were killed, including many civilians, after a faction of the armed forces tried to seize power using tanks and attack helicopters. Some strafed the headquarters of Turkish intelligence and parliament in the capital, Ankara, and others seized a major bridge in Istanbul.
Erdogan accused the coup plotters of trying to kill him and launched a purge of the armed forces, which last used force to stage a successful coup more than 30 years ago.
“They will pay a heavy price for this,” said Erdogan, who also saw off mass public protests against his rule three years ago. “This uprising is a gift from God to us because this will be a reason to cleanse our army.”