(Reuters) – The foreign ministers of Russia and Turkey spoke by telephone on Sunday, a day after Ankara angered Moscow by sending five Ukrainian commanders home with President Volodymyr Zelenskiy in what Russia called a violation of a prisoner exchange agreement.

The Russian and Turkish foreign ministries said Sergei Lavrov and Hakan Fidan discussed the situation in Ukraine, as well as a Black Sea grain export agreement that lifted a Russian de facto blockade of Ukrainian ports last year.

Moscow has threatened to quit the grain export deal when it comes up for renewal on July 17, saying demands to facilitate sales of its own grain and fertiliser have not been met.

Turkey’s President Tayyip Erdogan said on Saturday that he was pressing Russia to extend the deal, brokered last year by Ankara and the United Nations, by at least three months.

The Russian ministry said the two sides had focused on recent developments around Ukraine, including Ankara’s returning detained commanders of Ukraine’s Azov unit, which defended a steelworks in the Ukrainian port city of Mariupol last year.

Russia captured the city last year after laying it to waste, killing thousands of civilians in a three-month siege. The Azov unit led the city’s defence, holding out in the steelworks for weeks until they were ordered by Kyiv to surrender.

The captured Azov commanders, lionized as heroes in Ukraine and vilified in Russia, were released in a prisoner swap in September, under terms that required them to stay in Turkey until the war ends. Zelenskiy brought them home on Saturday after a visit to Turkey.

Kremlin spokesman Dmitry Peskov said on Saturday that Turkey had violated agreements in permitting their release, and had failed to notify Russia in advance.

Ankara has not commented publicly about the decision to send them home. Turkey’s presidency and foreign ministry did not respond to Reuters requests for comment.