The US struck Iran to respond to a drone attack a day earlier on a cargo ship in the Strait of Hormuz, a provocation that President Donald Trump said violated the ceasefire.
US Central Command said the military struck missile and drone locations and coastal radar sites in Iran on Friday.
The strikes came shortly after Mr Trump told reporters, “You’ll find out”, whether the US would response to the drone attack.
“I don’t like the fact that they took a shot yesterday, actually four of them,” Mr Trump said at the White House shortly before the US struck back.
When asked why there would be strikes when Mr Trump has insisted talks with Tehran are going well, Mr Trump said of Iran: “They’re a little bit different.”
He then abruptly cut off questions and reporters were ushered out of his office.
The British military said on Thursday that a container ship was hit a projectile off the coast of Oman, coming hours after Iran threatened vessels to stop using the route.
The United Kingdom Maritime Trade Operations centre said no injuries were reported.
The development came during a fragile time for the US and Iran as they work to negotiate a permanent end to the war.
Iran has increasingly challenged the region and the US over its control of the Strait of Hormuz, even with the current interim deal it reached with the US last week.
The attack on the cargo ship happened while a United Nations maritime agency was beginning an operation to move stranded ships out of the strait this week, using an alternative route, hugging the shores of Oman rather than sailing through the central part of the strait.
The International Maritime Organization halted the evacuations after the attack and said on Friday they will not resume until there are guarantees that the other ships will not be attacked.
About 115 ships were able to move out of the strait in recent days, leaving about 500 still in the area, said Arsenio Dominguez, the agency’s secretary-general.
The opening of the alternative passage through the strait was expected to relieve pressure on the world economy and remove Iran’s main source of leverage in ongoing peace talks with the US.
The US and Iran are still negotiating terms of the deal, including issues such as getting ships through the key strait and addressing the future of Iran’s stockpile of highly enriched uranium.
Under the interim deal, the two sides have 60 days to work out the details.
Shipping analysts said the drone strike cast a shadow over what had been a growing stream of trapped vessels finally leaving the Gulf and an increasing flow of tankers carrying crude oil.
“A week of widening commercial confidence in the Strait of Hormuz has hit its first significant test,” said marine data company Windward on X.
It said that while the strait remains operationally open with 43 transits recorded after the incident, “the pace of normalisation has slowed”.
On Wednesday before Thursday’s drone strike, 78 vessels transited the strait, the highest since the war began, although below the pre-war averages of 130 or more per day.
At least two tankers reversed course while attempting to transit the strait on the UN-backed route near Oman after Iran insisted vessels use only the Teheran-approved routes, according to marine data and analytic firm Lloyd’s List Intelligence.
More than two dozen ships were still transiting the strait’s southern route after the attack, Lloyd’s said on Friday.