French President Emmanuel Macron and Greek Prime Minister Kyriakos Mitsotakis say the agreement benefits both the EU and NATO by promoting security in the Mediterranean, North Africa, the Middle East and the Balkans.

Turkey, which has an uneasy history and relationship with its NATO neighbour Greece, has criticised the agreement as threatening "regional peace and stability".

The deal was backed by 191 MPs in the country's 300-member assembly. It got support from the ruling New Democracy party, Socialists, Movement of Change, and junior nationalist party Greek Solution.

Mitsotakis told parliament that the deal "shields" Greece "in a troubled Mediterranean", saying that Athens had been trying to secure such an agreement since 1974, when Turkey invaded neighbouring Cyprus that has a majority Greek-Cypriot population.

"In the event of an attack, our country will have the backing of the strongest army on our continent," the prime minister said.

The three Belharra frigates are to be delivered starting from 2025, in a deal to be finalised by the end of this year to the tune of three billion euros ($3.5 billion).

The main opposition left-wing Syriza party, which voted against the deal, has questioned clauses that require Greece to support French military operations in the war-torn Sahel in Africa and vowed to change this if it comes to power.

It also expressed doubts over whether the deal means France would provide support if there was a conflict between Greece and Turkey over its maritime zones.

Party leader and former prime minister Alexis Tsipras says the agreement embroils Athens in "particularly dangerous adventures" abroad and increases defence spending at the expense of the health budget during the coronavirus pandemic.

A Greek diplomatic source this week called the conflict-ridden Sahel "a potential time bomb for the Mediterranean".

In September 2020, Mitsotakis unveiled Greece's most ambitious arms purchase programme in decades after a dangerous standoff with Turkey over hydrocarbon resources and naval influence in the waters off their coasts.

A month earlier, Turkey had sent an exploration ship and a small navy flotilla to conduct seismic research in waters which Greece considers its own under postwar treaties.

In contrast to other EU and NATO allies, France strongly backed Greece and Cyprus at the time, sending warships and fighter jets to the eastern Mediterranean.