US and Israeli aircraft struck Iranian vessels south of Iran's Larak Island in the Strait of Hormuz, killing "several Iranian nationals," Iran's semi-official Fars news agency reported on Tuesday.

While the agency did not confirm the exact number of dead, some media reports said four people were killed in the strikes.

The reports come amid an ongoing ceasefire and increasing diplomatic efforts to bring the US-Israeli war on Iran to a permanent end.

On Tuesday, the US Secretary of State Marco Rubio said an agreement to end the war will "take a couple days" to finalise even as the parties inch closer to agreement on what it should look like.

"I think there's strong alignment and agreement on what a preliminary draft should look like. I think, like anything with something like this, it's going to take a couple days to settle on, even down to the disagreements over a word, sentence," Rubio, who also doubles as President Donald Trump's national security adviser, told reporters en route to New Delhi.

"If there's going to be a deal, we're going to have to work through that, but this is, you know, it's either going to be a good deal, or there isn't going to be one," he added.

Rubio continued to criticise Iran's efforts to shutter the Strait of Hormuz to commercial traffic, saying it is "unlawful, it's illegal, it's unsustainable."

"There's no country in the world that's in favour of the tolling system, except the regime in Iran. So that's not acceptable. That cannot happen," he said. "The straits need to be open, unimpeded, without tolls, and obviously that needs to happen."

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The US-Israeli war started with strikes on Iran on February 28 and was followed by Iranian retaliation targeting Israel and US allies in the Gulf as Tehran shuttered the Strait of Hormuz.

A ceasefire took effect on April 8 through Pakistani mediation, but talks in Islamabad failed to produce a lasting agreement.

Trump later extended the truce indefinitely while maintaining a blockade on vessels travelling to or from Iranian ports through the strategic waterway. Last week, he said the deal has been "largely negotiated" and awaits finalisation.

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