Donald Trump has launched a series of new strikes on Iran after issuing a "deal or no deal" ultimatum to the Islamic Republic.
US Central Command confirmed it had carried out numerous hits on the country's south in "self-defence" and to "protect our troops from threats posed by Iranian forces".
Centcom spokesman Captain Tim Hawkins said the strike took place near Bandar Abbas, home to an Iranian naval base near the Strait of Hormuz.
He added that targets included missile launch sites and Iranian boats trying to place mines.
The strikes were taken "while using restraint during the ongoing ceasefire", Captain Hawkins said.
Several explosions were heard in Bandar Abbas shortly after 9pm BST, according to Iranian state media.
Similar sounds were heard at the same time around the cities of Sirik and Jask, according to the report.
In a statement, Iran's Islamic Revolutionary Guard Corps said it had activated its air defencea to "counter hostile targets".
The IRGC said earlier that its forces had destroyed a "hostile" drone, according to CNN.
Marco Rubio, the US Secretary of State, was then pressed on the strikes early this morning.
He branded Iran's chokehold over the strait "unlawful", "illegal", and "unsustainable for the world".
Donald Trump said negotiations were 'proceeding nicely' as he issued his 'deal or no deal' ultimatum
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Mr Rubio then vowed that the waterway would be cleared by any means necessary, saying: "The straits have to be open... They're going to be open one way or the other."
The US attack came just as peace talks looked to finally be nearing a climax.
Earlier, the President had said negotiations with Iran were "proceeding nicely" and called for a number of countries in the Middle East to sign the Abraham Accords - which would see them formally recognise Israel and engage in diplomatic relations.
On social media, Mr Trump said: "It will only be a great deal for all or, no deal at all - back to the battlefront and shooting, but bigger and stronger than ever before - and nobody wants that!"
Mr Trump met leaders from Saudi Arabia, the UAE, Qatar, Pakistan, Turkey, Egypt, Jordan, and Bahrain on Saturday and called for non-signatory countries to sign the accords.
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Marco Rubio said there were 'pretty solid things on the table' in regard to Iran's ability to open up the Strait of Hormuz
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He said the agreement, currently signed by Bahrain, Morocco, Sudan, Kazakhstan, and the UAE, would be a "document respected like no other that has ever been signed".
He also called for Iran to sign the accords, an act Mr Trump said would be "something special".
A Pakistani source familiar with the matter said the President was using talks with Iran to push the Abraham Accords - but added the two issues were "note interlinked and cannot be made so".
Shortly before the strikes were made public, Mr Trump said enriched uranium or "nuclear dust" would be "immediately turned over to the United States to be brought home and destroyed", or would be destroyed in place with the cooperation of Iran and the Atomic Energy Commission.
Though on Sunday, a senior White House figure said Iran had already agreed to turn over its nuclear stockpile.
Esmail Baghaei said some progress in talks had been made, but a deal was not 'imminent'
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Mr Trump had previously suggested both sides were close to a deal.
Foreign Ministry spokesman Esmail Baghaei said some progress had been made, but a deal was not imminent.
He said: "It is correct to say that we have reached a conclusion on a large portion of the issues under discussion... But to say that this means the signing of an agreement is imminent - no-one can make such a claim."
Mr Rubio earlier said diplomacy would be given every chance before considering to deal with the issue in "another way".
He added there were "pretty solid things on the table" in regard to Iran's ability to open up the Strait of Hormuz - which a fifth of the world's oil flowed through before Iran implemented its blockade.
Mr Baghaei said nuclear issues would only be discussed if a framework was agreed on first.
While Mr Trump has long said his goal is to prevent Iran from developing a nuclear weapon - and has framed that as the reason behind both this year's Operation Epic Fury and last summer's Operation Midnight Hammer.