Turkey and the United States conducted joint naval exercises in the Black Sea on Tuesday, prompting objections from Russia.

Axar.az reports that the military drills have “further strengthened cooperation between the naval forces of the two countries and has contributed to their interoperability,” the Turkish Defence Ministry said on Wednesday.

Relations between NATO allies Turkey and the United States have worsened in recent years over Turkey's purchase of S-400 air defence missiles from Russia, which Washington maintains are incompatible with the NATO alliance's defence systems. Turkey has also intervened in Syria to battle Kurdish militants allied with the United States against Islamic State (ISIS).

Two Turkish frigates, TCG TURGUTREİS and TCG ORUCREİS and two U.S. destroyers, USS PORTER and USS DONALD COOK participated in the maritime drills, alongside two Turkish F-16 jets and one U.S. maritime patrol aircraft, the Turkish Defence Ministry said.