President Recep Tayyip Erdoğan held talks with his Ukrainian counterpart Volodymyr Zelenskyy, who arrived in Istanbul on Friday.
The closed-door meeting took place at the Dolmabahçe Office in the Beşiktaş district.
The two presidents are expected to hold a joint news conference later.
President Erdoğan was expected to press for negotiations to end Russia's war in Ukraine, now in its third year, an unnamed Turkish government official said.
The official said talks would also focus on a possible new measure guaranteeing the navigational safety of commercial vessels in the Black Sea. The official spoke on condition of anonymity in line with Turkish government protocol.
In a message he posted on X, Zelenskyy expressed appreciation for Türkiye's reliable support for Ukraine.
"Both of our countries, the entire region, and global food security require unconditional security of navigation in the Black Sea" he said, as he highlighted the importance of cooperation in this regard.
"We also require Türkiye’s assistance in releasing our prisoners of war and all of our people, including Crimean Tatars, held captive by Russia," the Ukrainian president said.
The visit comes as Zelenskyy and other officials continue to press other nations for more munitions and weaponry to halt the advance of Russian troops trying to make deeper gains into the Ukraine-held western part of the Donetsk region and also penetrating the Kharkiv region north of it.
Ukrainian Foreign Minister Dmytro Kuleba said in Vilnius, Lithuania, where he attended a meeting of the foreign ministers of France, Lithuania, Latvia and Estonia, that "drop by drop" aid to Ukraine no longer works.
"If things continue as they currently happen, it's not going to end well for all of us," Kuleba said. "What is required is an unrestricted and timely supply of all types of weapons and ammunition to ensure that Ukraine beats Russia and the war in Europe does not spill over."
Türkiye has positioned itself as an intermediary in the Russia-Ukraine conflict and Erdoğan was a key player in brokering the Black Sea Grain Initiative.
Shortly after Russia's full-scale invasion of Ukraine in February 2022, Türkiye hosted a meeting between the Russian and Ukrainian foreign ministers as well as unsuccessful talks between negotiators from the two countries aimed at ending the hostilities.
Ukraine has been defending itself against a full-scale Russian invasion for more than two years. For its campaign, Kyiv has received massive international support, mostly from Western allies, in the form of weapons deliveries, humanitarian aid, and sanctions against Russia.
Türkiye was a key player in the now-on-hold deal that allowed for the safe passage of Ukrainian grain shipments via the Black Sea despite the blockade of its ports after Moscow launched its invasion in late February 2022.
The accord, brokered by Ankara and the United Nations in July 2022, ended after Moscow refused to renew it. Ankara has ramped up efforts to try to revive the initiative.
Moscow withdrew from the accord on July 17, accusing the West of hampering its grain and fertilizer exports. It has since attacked Ukrainian agricultural and port infrastructure. Moscow has said that it was ready to return to the deal once an accompanying agreement concerning Russia was implemented.
Zelenskyy visited the shipyards in Istanbul, where Turkish companies are building two corvettes for the Ukrainian navy.
Zelenskyy last visited Türkiye last July, when he returned to Ukraine with a group of Ukrainian commanders who were in Türkiye following a prison exchange deal and were to remain on Turkish territory until the end of the war. There was no explanation from Ankara or Kyiv about why they were allowed to return to Ukraine.
