A new defense agreement between Greece and France will allow them to come to each other's aid in the event of an external threat, Greek Prime Minister Kyriakos Mitsotakis said on Thursday, amid increased tensions with Turkey, Reuters reports.

The strategic military and defence cooperation pact between the two NATO allies was clinched last month and includes an order for three French frigates worth about 3 billion euros.

Athens had already ordered some 24 Dassault-made Rafale fighter jets this year.

"For the first time it is clearly stipulated that there be military assistance in the event of a third party attacking one of the two states. And we all know who is threatening whom with a casus belli (cause for war) in the Mediterranean," Mitsotakis said, in a clear reference to Turkey.