Turkey is set to implement an international convention on naval passage through two of its strategic straits, which would allow it to limit the movement of Russian warships between the Mediterranean Sea and the Black Sea.
Mevlut Cavusoglu, Turkey's foreign minister, said on Sunday that the situation in Ukraine had become a war, a declaration that authorizes Ankara to activate the Montreux Convention and ban Russian war vessels from entering the Black Sea through the Bosporus and Dardanelles straits.
"In the beginning, it was a Russian attack," Cavusoglu said in an interview with broadcaster CNN Turkish. "Now it has turned into a war."
"Turkey will implement all provisions of Montreux Convention in a transparent manner," he added.
The decision comes three days after Kyiv had asked Ankara to close the Bosporus and Dardanelles straits to Russian ships.
But what does the Montreux Convention entail and how could its implementation affect the war between Russia and Ukraine?
The only passage to the Black Sea
The Bosporus and Dardanelles straits, also known as the Turkish Straits or the Black Sea Straits, connect the Aegean Sea and the Black Sea via the Sea of Marmara. It is the only passage through which Black Sea ports can access the Mediterranean and beyond.