Greek Prime Minister Alexis Tsipras said that Athens would continue its joint efforts with other NATO states to improve alliance’s capabilities over the whole operational area in the Aegean Sea.

Athens will not tolerate the actions of Ankara violating country’s sovereignty in the Aegean Sea, Greek Prime Minister Alexis Tsipras said Friday.

NATO ships have been deployed to the Aegean Sea for months to monitor migrant flows between Turkey and Greece. Athens claim that Ankara refuses NATO ships to enter the maritime zone near some of the Greek islands, as Turkey considers them as its own territory.

“Greece will not tolerate any actions that challenge our sovereignty,” Tsipras said at a meeting with NATO Secretary General Jens Stoltenberg, as quoted by the Proto Thema newspaper.

He added that Athens would continue its joint efforts with other NATO states to improve alliance’s capabilities over the whole operational area in the Aegean Sea.

The EU states are currently struggling to deal with a refugee influx, with hundreds of thousands of people fleeing conflict-torn countries in the Middle East and North Africa. The Aegean Sea is one of the main transit routes for refugees heading for Greece from the Turkish territory.