US President Donald Trump says a ceasefire is still in place with Iran, despite a clash between Iran and US naval destroyers in the Strait of Hormuz for which both sides blamed the other.
The US said Iran launched missiles, drones and small boats against three of its warships, in what it called an "unprovoked attack". Trump said Iran "trifled with us today".
Iran's top military command, meanwhile, alleged the US had targeted an Iranian oil tanker and another vessel approaching the Strait of Hormuz and carried out "aerial attacks" on several coastal areas.
The flare-up comes a day after Iran's foreign ministry had said it was considering a US proposal to end the war.
In a further sign of the fragility of the ceasefire, early on Friday the United Arab Emirates' Ministry of Defence said its air defences were "actively engaging" with a missile and drone attack from Iran.
The ministry later said two ballistic missiles and three UAVs had been launched from Iran, resulting in three “moderate injuries”.
Iranian state media initially reported "explosions" in the Strait of Hormuz on Friday, describing them as an "exchange of fire" with the "enemy". Meanwhile, local media reported explosions were heard in Tehran.
Not long after, a statement from Iran's top military command said US "aerial attacks" struck the coasts of Bandar Khamir, Sirik and Qeshm Island.
It said it responded immediately by attacking US military vessels, inflicting "significant damage", and accused the US of a "violation of the ceasefire".
US Central Command (Centcom) described the Iranian attacks as "unprovoked", saying Iranian forces launched "multiple missiles, drones and small boats" as US Navy guided-missile destroyers transited through the strait.
Centcom said it had "eliminated inbound threats and targeted Iranian military facilities responsible for attacking US forces, including missile and drone launch sites; command and control locations; and intelligence, surveillance and reconnaissance nodes."
"Centcom does not seek escalation but remains positioned and ready to protect American forces," the statement continued.
Posting on Truth Social, Trump said that the US had destroyed multiple small boats, missiles and drones, adding that "great damage" was "done to the Iranian attackers".
The US president also reiterated a warning over the peace deal: "Just like we knocked them out again today, we'll knock them out a lot harder, and a lot more violently, in the future, if they don't get their Deal signed, FAST!"
In a statement on X, Iranian Foreign Minister Abbas Araghchi said: “Every time a diplomatic solution is on the table, the US opts for a reckless military adventure.”
He added: “Whatever the causes, the outcome is the same: Iranians never bow to pressure and diplomacy is always the victim.”
An Israeli source told the BBC there was "no Israeli involvement" in the latest attacks.
The increase in tensions comes despite the US president saying in recent days that the war in Iran will be "over quickly".
US news outlet Axios had said that the White House believes it could be closing in on a 14-point memorandum of understanding with Iran, which could set a framework for more detailed nuclear negotiations.
On Wednesday, an Iranian foreign ministry spokesman said the latest US proposal was being considered and that Tehran would share its views with Pakistani mediators.
Pakistan's foreign minister said his country was "endeavouring to convert this ceasefire into a permanent end to this war".
But a senior member of Iran's parliament has dismissed the 14-point memorandum of understanding as a "wish list".
The spokesperson of the Iranian parliament's national security and foreign policy commission, Ebrahim Rezaei, wrote on X that Iran "has its finger on the trigger", warning Iran would "deliver a harsh and regret-inducing response" if the US did not "surrender and grant necessary conditions".
Both the US and Iran have threatened an escalation in violence if their respective conditions for a peace deal aren't met.
In a Truth Social post on 6 May, Trump wrote that if Iran did not agree to a deal "the bombing starts, and it will be, sadly, at a much higher level and intensity than it was before".
Trump had previously said Operation Epic Fury - the initial US-Israeli offensive in Iran - would come to an end "assuming Iran agrees to give what has been agreed to". Prior to this statement, US Secretary of State Marco Rubio had said the operation was over and had achieved its objectives.
Trump also said, not for the first time, that Iran had agreed to never have a nuclear weapon "among other things" - a claim that has not been confirmed by Tehran. Iran's nuclear programme has been one of the key sticking points between the two sides.
