Greece's Supreme Court has ruled against extraditing eight Turkish soldiers whom the Turkish government accuses of being involved in last July's attempted coup.
The eight men fled in a helicopter to Greece after the coup attempt but say they were not involved.
Presiding judge Giorgos Sakkas said the men were unlikely to receive a fair trial in Turkey.
Turkey's said the decision appeared to be politically motivated.
"We protest this decision which prevents these individuals who have threatened the life of our president and took an active role in a coup attempt that killed 248 of our citizens... from
appearing in front of Turkish judiciary," the Turkish foreign ministry said in a statement.
"Once again Greece, an ally and a neighbour, has failed to fulfil the basics of the fight against terrorism."
The case has presented a diplomatic dilemma for Greece and created new tensions between the two Nato allies. They have a complex relationship and are currently working together to help negotiate a peace deal in divided Cyprus.
Justice Minister Stavros Kontonis said before the verdict that he would respect the decision and not intervene.
Turkey has demanded the men, whom it calls traitors, be returned to stand trial. The soldiers - three majors, three captains and two sergeant majors - argue their lives would be in danger.
The eight soldiers in Greece have said that their relatives in Turkey have lost jobs and had their passports confiscated.
In the wake of the coup attempt, tens of thousands of people from every level of Turkish society have been purged from their jobs, including military officers, government officials and schoolteachers.
Critics of President Recep Tayyip Erdogan say he has used the failed uprising as a way of removing his opponents and tightening his hold on power.
The Turkish government says that it has taken legitimate action to root out "terrorist" groups that had infiltrated the state.
It blamed US-based Islamic cleric Fethullah Gulen, who leads a mass movement in Turkey, for the bloody coup attempt. He denies any involvement.
Soon after the soldiers arrived in Greece, they were given two-month suspended prison sentences for illegally entering the country.
'A scandal' - Turkish media respond to the ruling, by Pinar Sevinclidir, BBC Monitoring
Pro-government news outlets have branded the decision "a scandal " and accused Greece of "protecting the coup soldiers".
Yeni Safak daily said Greece was taking the plotters under its wing and Aksam newspaper called the ruling "a historical disgrace"
A Haber TV report hinted at a diplomatic crisis, saying " the relationship between Turkey and Greece will change after this decision".
