A Russian warship fired warning shots on Sunday at a cargo ship in the Black Sea that was headed to Ukraine, the first such incident since Russia left the UN-brokered grain deal, which had guaranteed safe passage for ships exporting goods from Ukraine, despite the ongoing war. 

Russia’s Defense Ministry said in a statement to Tass, its state news agency, that it fired warning shots after the cargo ship would not stop for inspection. After the ship was “forcibly stopped” and inspected, it continued to its destination, the Ukrainian port of Izmail.

“The dry cargo ship’s captain did not respond to the demand to stop for an inspection of the potential carriage of prohibited goods. The Russian combat ship fired warning shots from automatic small arms to forcibly stop the vessel,” Russia’s defense ministry said in the statement. 

The ministry said the incident took place at about 6:40 a.m. local time, after the patrol ship “detected the Palau-flagged dry cargo ship Sukru Okan.”

A Ka-29 helicopter with Russian servicemen responded, according to the statement, and subsequently searched the ship.

Mykhailo Podolyak, senior adviser to Ukrainian President Volodymyr Zelensky, described the incident as a “deliberate attack” and a “clear violation of international law of the sea, an act of piracy and a crime against civilian vessels of a third country in the waters of other states.”

“Ukraine will draw all the necessary conclusions and choose the best possible response,” Podolyak continued, in the statement on X, formerly known as Twitter.

The incident comes after last month Russia left the grain-export deal, brokered by the United Nations and Turkey, repeating claims that it wasn’t getting enough benefit from the deal. The grain deal has been hugely consequential in reducing world hunger and stabilizing the global economy, as much of the world depends on Ukraine for its grain. 

Last week, Zelensky announced “humanitarian corridors” in the Black Sea to allow for civilian cargo ships that have been stuck since the beginning of the war in February 2022 to be released. Some expressed concerns about the safety of traveling through the corridors as it remains unclear how Russia would respond.