Washington DC - President Donald Trump lashed out at Israel on Tuesday morning and warned it not to break newly-agreed ceasefire with Iran, amid reports of ongoing fighting.

In a fast-moving series of declarations, the 79-year-old Republican, who was on his way to attend a NATO summit in The Hague, said on Truth Social the ceasefire he announced had come into effect.

"ISRAEL is not going to attack Iran. All planes will turn around and head home, while doing a friendly 'Plane Wave' to Iran. Nobody will be hurt," Trump wrote.

Minutes earlier, he had singled out Israel in a furious response to allegations that both sides had already violated the deal.

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"I'm not happy with them," he told reporters on the White House lawn. "I'm not happy with Iran either. But I'm really unhappy if Israel is going out this morning."

"I've got to get Israel to calm down," Trump continued. "Israel, as soon as we made the deal, they came out and dropped a load of bombs the likes of which I've never seen before."

The two countries have been "fighting so long and so hard that they don't know what the f*** they're doing, do you understand that?" the president added.

Trump's unusually public display of anger at Israel saw the US leader apparently trying to cajole his ally to call off warplanes in real time.

Earlier the same morning, he had posted on Truth Social: "ISRAEL. DO NOT DROP THOSE BOMBS" – without it being clear which bombs he was referring to.

"IF YOU DO IT IS A MAJOR VIOLATION. BRING YOUR PILOTS HOME, NOW!"

Israel had accused Iran of launching missiles after the ceasefire came into effect, which Tehran categorically denied.

With full US backing, Israel launched an unprovoked attack on Iran on June 13. As the sides exchanged missiles on a daily basis, the US officially joined the fray by bombing Iranian nuclear sites in an unprecedented aggression. Tehran on Monday responded with a retaliatory but largely symbolic strike on a major US air base in Qatar.