Tehran intensified its diplomatic stance following the deadly attack on Iranian vessel in the Caspian Sea initiated by Ukraine.

Ebrahim Azizi, chairman of Parliament’s National Security and Foreign Policy Commission on Monday warned that the attack would not go unanswered.

“Any attack on Iran will always come with a cost… Ukraine too may soon come to understand that Iran does not let actions go unanswered,” Azizi wrote in a post on X, describing the strike as “miscalculated.”

Earlier on Sunday, Foreign Minister Abbas Araqchi condemned the attack as a violation of the United Nations Charter and urged the international community to take action.

In separate conversations with European Union foreign policy chief Kaja Kallas and Russian Foreign Minister Sergey Lavrov, Araqchi denounced what Tehran described as a Ukrainian military attack on an Iranian civilian vessel. According to Iran’s Foreign Ministry, he called for a “firm response” from the UN Security Council, the European Union and the wider international community.

The diplomatic row intensified after Iran summoned Ukraine’s chargé d’affaires in Tehran to lodge a formal protest over what it described as a “hostile and criminal act.” In its condemnation, Iran’s Foreign Ministry reiterated that Tehran has never intervened in the Russia- Ukraine conflict.

Iranian authorities said one sailor was killed and several others were injured when the vessel came under attack in the Caspian Sea.