President Volodymyr Zelensky held a phone call with his Turkish counterpart Recep Tayyip Erdogan on Jan. 5, discussing Ukraine's peace formula, defense cooperation, and security in the Black Sea, among other topics, the Presidential Office reported.

"The mediation of Turkey is crucial so that it is possible to release the Crimean Tatars and all others - adults and children, soldiers and civilians - who are held in Russian captivity," Zelensky added.

The two leaders agreed to strengthen the Ukrainian-Turkish cooperation in the high-tech sphere, in particular, the creation of joint defense enterprises and joint production of military equipment, according to the Presidential Office.