The U.S. strikes came after a cargo ship was attacked in the Strait of Hormuz.
President Donald Trump announced "major combat operations" against Iran on Feb. 28, with massive joint U.S.-Israeli strikes targeting military, government and infrastructure sites.
Delegations from the U.S. and Iran entered negotiations last month aimed at a war-ending deal based on a memorandum of understanding signed by both countries.
The U.S. and Iran have nonetheless continued to exchange relatively limited strikes despite the signing of the memorandum and amid the continuation of peace talks.
On Sunday, Iranian forces fired on commercial vessels in the Strait of Hormuz while U.S. forces were conducting strikes on Iranian targets, according to a U.S. official.
The official added that U.S. aircraft shot down an Iranian cruise missile and a one-way attack drone that were targeting the vessels. It’s unclear whether any vessels were damaged in those attacks.
-ABC News' Steven Beynon
Following a wave of U.S. strikes on Iranian targets on Sunday, Iranian Deputy Foreign Minister Kazem Gharibabadi released a statement, saying, "No action against Iran should go unanswered."
A spokesperson for the foreign minister also called the U.S and Israel's attacks "the continuation of a blatant and unprovoked act of aggression."
Addressing Iran's strikes on American assets in the Middle East, the spokesperson said, "Iran’s strikes on U.S. military bases and assets stationed in the southern Persian Gulf constitute a legitimate and lawful exercise of its inherent right to self-defense under international law."
The U.S. conducted a new round of strikes on Iranian targets on Sunday, a U.S. official told ABC News.
The targets included Iranian air defense systems and IRGC small boats around the Strait of Hormuz, the official said.
The strikes were intended to degrade Iran’s ability to target commercial shipping, according to the official, who said no U.S. troops were wounded in the attacks.
-ABC News' Steve Beynon
United Nations Secretary-General Antonio Guterres said he's “deeply concerned" by the increasing attacks in Iran and warned of "catastrophic consequences" globally should parties return to "full-scale hostilities."
"I am deeply concerned by the serious escalation & renewed military confrontations in the Gulf, including the Iranian attacks on ships in the Strait of Hormuz, the attacks by the US on Iran, and the attacks by Iran on targets in the neighboring countries," Guterres wrote in a post on X Sunday. "These attacks must all stop."
"A return to full-scale hostilities would have catastrophic consequences – for the peoples of the region, for international peace & security & for the global economy. I urge Iran & the US to urgently resume negotiations & to address outstanding issues through diplomacy," Guterres further wrote.
-ABC News Claire Bower
