Iranian Foreign Minister Abbas Araghchi on Sunday said Ukraine's attack on an Iranian commercial vessel in the Caspian Sea, which killed a sailor, "cannot go unanswered," warning that Tehran would respond to what it described as a violation of international law.
In a post on X, Araghchi condemned the strike, saying the attack on a civilian vessel was "a crime" and that those responsible would be held accountable.
"The Ukrainian regime's attack on an Iranian commercial vessel in the Caspian Sea, resulting in the martyrdom of one of our sailors, cannot go unanswered," Araghchi said.
Araghchi's remarks came a day after Iran said a Ukrainian strike targeted an Iranian commercial vessel in the Caspian Sea, causing an explosion that killed one sailor and wounded another.
Iranian authorities condemned the attack as a "hostile and criminal" act, summoned Ukraine's charge d'affaires in Tehran to protest the incident and accused Kyiv of expanding the war beyond Ukraine's borders.
Ukrainian President Volodymyr Zelenskyy said Ukrainian forces had struck Russian vessels transporting Iranian-linked military cargo in the Caspian Sea.
Ukrainian officials said the targeted ship was carrying components for drones and missiles intended for Russia's war effort. Iran has denied those allegations, maintaining that the vessel was a commercial ship.
The Caspian Sea is bordered by Iran, Russia, Kazakhstan, Turkmenistan and Azerbaijan and has generally remained outside the direct battlefield of Russia's war in Ukraine.
Iran has rejected allegations that it supplies weapons for use in Russia's war against Ukraine, while Ukraine has increasingly targeted military assets and supply chains that it says contribute to Russia's military capabilities.