A ceasefire between Iran and the United States was teetering as the two countries traded fire over the strategic Strait of Hormuz and the United Arab Emirates reported attacks for the first time since the truce was declared nearly a month ago.
A day after US President Donald Trump announced an operation to escort trapped vessels through the strait, Fox News quoted him as threatening that Iran would be "blown off the face of the earth" if it attacks US ships.
Iran appeared undaunted as it vowed to keep exerting control over the Strait of Hormuz, the narrow waterway through which one-fifth of the world's oil flowed before the United States and Israel attacked Iran on 28 February.
A US admiral said US forces sank six small Iranian ships. Iran denied any had been sunk and earlier fired warning shots at US warships.
The UAE, a close US ally and key Arab partner of Israel, said it came under a barrage of missiles and drones from Iran.
"These attacks represent a dangerous escalation and an unacceptable transgression, posing a direct threat to the state's security, stability, and the safety of its territories," the UAE's foreign ministry said in a statement.
A strike targeting an energy installation in the emirate of Fujairah injured three Indian nationals, UAE authorities said.
They said four cruise missiles were launched, with three successfully shot down and another falling into the sea.
Iran also fired drones at a tanker affiliated with the UAE's state-owned oil giant ADNOC, authorities said.
A senior Iranian military official did not deny the strikes but said the Islamic republic had "no pre-planned programme to attack the oil facilities in question".
"What happened was the product of the US military's adventurism to create a passage for ships to illegally pass through" the Strait of Hormuz, the official said, according to state television.
"The US military must be held accountable for it."
Iranian Foreign Minister Abbas Araghchi - seen as a moderate in the cleric-run state - said the latest clashes showed there was "no military solution to a political crisis" and pointed to Pakistan's efforts to keep mediating.
"The US should be wary of being dragged back into quagmire by ill-wishers. So should the UAE. Project Freedom is Project Deadlock," he wrote on X.
Meanwhile, world leaders have piled pressure on Tehran to stick to diplomacy to bring an end to the Middle East war.
German Chancellor Friedrich Merz implored Tehran to "return to the negotiating table and stop holding the region and the world hostage", echoing calls from French President Emmanuel Macron and British Prime Minister Keir Starmer.
Saudi Arabia, a key US ally whose energy infrastructure has been hit by Iran, has joined the calls to de-escalate and called for "diplomatic efforts to reach a political solution".
US flexes muscle in strait
Mr Trump has repeatedly demanded that Iran reopen the strait - which was open before the war and which Tehran considers a main point of leverage.
On Sunday, he announced what he called "Project Freedom" to guide ships from neutral countries out of the Gulf, saying it was a humanitarian effort to help stranded crews.
Much remained unclear about how the plan would operate and how the United States would assist.
US Central Command said yesterday that guided-missile destroyers had transited Hormuz and that, as a first step in the project, two US-flagged merchant vessels had travelled out.
But Iran's Revolutionary Guards denied the claim, saying: "No commercial vessels or oil tankers have passed through the Strait of Hormuz in the past few hours."
Seoul said yesterday that an "explosion and fire" had also struck a South Korean ship in the strait.
Meanwhile, Denmark's freight giant Maersk has said that one of its ships has successfully sailed through the Strait of Hormuz under US escort.
The ship, US-flagged Alliance Fairfax, had been stuck in the Gulf since the war erupted in February and was "offered the opportunity" to leave accompanied by the US military.
"The vessel subsequently exited the Persian Gulf accompanied by US military assets" on 4 May, the company said in a statement.
"The transit was completed without incident, and all crew members are safe and unharmed."
As of 29 April, more than 900 commercial vessels were located in the Gulf, according to maritime intelligence firm AXSMarine.
Mr Trump appeared to play down the Iranian strikes, writing on social media that Iran had "taken some shots" but that it caused little damage.
Oil prices climbed further after the attacks, with the benchmark international contract Brent crude for July delivery jumping more than 5%.
Soaring energy costs for consumers due to the war have caused economic pain around the world and created a political headache for Mr Trump months before congressional elections.
In Lebanon, a separate ceasefire with Israel aimed at halting fighting with Iran-backed armed group Hezbollah also faced further strain yesterday.
Hezbollah and Israeli troops clashed in southern Lebanon, with Israel reporting moderate injuries to two of its soldiers.
Israel has heavily bombed and invaded southern Lebanon in response to aerial attacks by Hezbollah that dragged Lebanon into the war in early March.
Israeli strikes have killed more than 2,700 people since the fighting began, according to Lebanon's health ministry.
Lebanese President Joseph Aoun has called for a security deal and an end to Israeli attacks before any meeting with Israeli Prime Minister Benjamin Netanyahu, a potentially historic encounter which Mr Trump has proposed should take place this month at the White House.
