US and Iranian forces clashed in the Gulf, but President Donald Trump said a ceasefire was still holding despite the flare-up, which dented hopes for a swift diplomatic resolution to the crisis.
The escalation came as Washington awaited Tehran's response to a US proposal to end the war, which began on February 28 when the US and Israel launched airstrikes on Iran.
Trump said on Thursday three US Navy destroyers were attacked as they moved through the Strait of Hormuz, a conduit for around a fifth of the world's oil and liquefied natural gas flows that Iran has all but closed since the conflict began.
"Three World Class American Destroyers just transited, very successfully, out of the Strait of Hormuz, under fire. There was no damage done to the three Destroyers, but great damage done to the Iranian attackers," Trump wrote on Truth Social.
He later told reporters the ceasefire remained in effect and played down the exchange.
"They trifled with us today. We blew them away," Trump said in Washington.
Iran, however, accused the United States of breaching the ceasefire, an agreement that has been punctuated by intermittent clashes since it was announced on April 7.
Iran's top joint military command said US forces had targeted an Iranian oil tanker and another ship, and carried out air attacks on civilian areas on Qeshm Island in the Strait of Hormuz and nearby coastal areas. It said Iranian forces responded by attacking US military vessels east of the strait and south of the port of Chabahar.
A spokesperson for Iran's Khatam al-Anbiya Central Headquarters said the Iranian strikes inflicted "significant damage," but US Central Command said none of its assets were hit.
Iranian state media later signaled a de-escalation, with Press TV reporting that, after several hours of exchanges, "the situation on Iranian islands and coastal cities by the Strait of Hormuz is back to normal now."
