It said the strikes were aimed at degrading Iran's ability to threaten freedom of navigation in the Strait of Hormuz.
"The United States is holding Iran accountable for recent unjustified aggression against commercial shipping and civilian crews freely navigating a vital international waterway," US Central Command wrote in a post on X.
Speaking on the sidelines of a NATO summit in Ankara, Trump earlier criticised Iranian officials for what he described as not sticking to the deals they negotiated and warned that the United States will likely engage in additional strikes on Wednesday night after US forces carried out attacks the previous day.
"I'll give a little warning: we're going to hit them hard tonight but we'll see how it all works out," Trump told reporters at the NATO summit in Turkey before his meeting with Ukrainian President Volodymyr Zelenskiy.
In earlier comments to reporters in Ankara, Trump said a memorandum of understanding that served as an initial ceasefire deal between the United States and Iran was over.
"For me, I think it's over," Trump said when asked about the status of the ceasefire.
He added that US representatives can continue negotiations but he cast doubt on the outcome.
"They can talk but I think they're wasting their time," he said.
But Trump on Wednesday said he did not think a full-fledged conflict with Iran would erupt after military strikes from both sides.
"I don't think it's going to start again. I think it's going to go very quickly. They hit a couple of ships, and so we hit them much harder," Trump told reporters after the NATO summit.
"Anything that happens is going to be over very quickly ... and will only make it safer, including for oil," he said.
He repeated his war aim that Iran can never have a nuclear weapon but suggested that goal may need to be achieved without a deal.
"They'll never build a nuclear weapon under our deal but I don't know if we're going to have a deal. We may just do it without a deal, because you know what, it's easier, because these people, they lie and they cheat," Trump said.
Eight members of the Iranian army were killed in the initial US attacks on southern parts of Iran early on Wednesday, state media reported.
The victims belonged to the air force and navy and died due to strikes in Bandar Abbas and Bushehr, it added.
Iran's English-language state broadcaster Press TV, citing what it described as a well-informed security source, said Iran was prepared to fight to maintain control over the Strait of Hormuz and would launch further attacks in response to US military action.
Iran would make no distinction between the United States and its regional allies, the report said.
In a flare-up of hostilities that pushed oil prices up sharply, Iran earlier said it had targeted US military sites in Bahrain and Kuwait after US forces struck Iranian targets in response to attacks on tankers in the Strait of Hormuz.
The renewed hostilities have also heightened safety and security concerns around the Strait of Hormuz, with shipping data showing at least four oil and gas tankers had turned back rather than try to transit the waterway - a vital supply route.
with AP and DPA
