Iran's deputy parliament speaker has warned Ukraine that any "mischievous" act in the region or the Caspian Sea will be met with a "regret-inducing" response from Tehran.

Hamid-Reza Haji Babaei issued the stark warning on Monday following a direct Ukrainian military attack against an Iranian civilian commercial vessel operating in the sovereign waters of the Caspian Sea over the weekend. The strike triggered an explosion aboard the merchant ship, resulting in the killing of one Iranian sailor and leaving another severely wounded.

"We warn Ukraine's masters that any mischief through your stooge in the region and the Caspian Sea will be met with a regret-inducing response from the great Iranian nation," Haji Babaei said.

Following the strike, Iranian Foreign Minister Abbas Araghchi initiated urgent high-level diplomatic outreach, holding a phone call with European Union Foreign Policy Chief Kaja Kallas. During the discussion, Tehran's top diplomat strongly condemned the Ukrainian military’s assault on civilian infrastructure. He urged the United Nations Security Council, the European Union, and the broader international community to issue an unequivocal condemnation of Kyiv’s aggression, insisting that the perpetrators, instigators, and foreign supporters of the strike be held fully accountable.

Araghchi also issued a sharp rebuke on X late Sunday, directly targeting Ukrainian President Volodymyr Zelenskyy: He said, “Zelenskyy has attacked an Iranian commercial vessel, killing a sailor. A blatant UN Charter violation done at Israel's behest to drag Europe into its war. In calls with EU High Rep Kallas and FM Lavrov, made clear that what the freeloader in Kyiv did CANNOT GO UNANSWERED.”

Concurrently, Iran’s Foreign Ministry summoned Ukraine’s chargé d’affaires to deliver an official, strong protest against Kyiv's action, reiterating that attacks targeting the lives, property, and trade routes of Iranian citizens will not be tolerated.