Iran has claimed Donald Trump’s threat to attack its civilian infrastructure “constitute war crimes”.

The president threatened to strike Iranian power plants and bridges in a foul-mouthed rant on Sunday if Tehran did not open the Strait of Hormuz.

Approximately one fifth of the world’s oil supply passes through the waterway, but Iran effectively blocked the shipping lane after the US and Israeli bombings against the country began at the end of February.

Subsequent economic pressure has seen the president grow increasingly irate.

He said on Saturday that “all hell would reign down” if Tehran did not re-open the strait within 48 hours, and on Sunday he listed all of the civilian targets the US would go after.

He said: “Tuesday will be Power Plant Day, and Bridge Day, all wrapped up in one, in Iran. There will be nothing like it!!! Open the Fuckin’ Strait, you crazy bastards, or you’ll be living in Hell – JUST WATCH! Praise be to Allah.”

Iran’s deputy foreign minister Kazem Gharibabadi claimed on Monday that Trump’s threats “constitute war crimes” and a “flagrant violation of Article 2(4) of the United Nations Charter”.

He added that Iran will deliver a “decisive, immediate and regret-inducing response to any aggression or imminent threat”.

An earlier statement from the spokesperson for Iran’s highest operational military command unit, Khatam al-Anbiya Central Headquarters, also warned: “If attacks on civilian targets are repeated, the next stages of offensive and retaliatory operations will be much more devastating and widespread.”

Tom Fletcher, the UN’s under-secretary general for humanitarian affairs told the BBC: “This stuff isn’t negotiable. You don’t hit civilian infrastructure. You don’t hit schools, you don’t hit energy sources, you don’t hit bridges. Those are war crimes. That is absolutely clear in international law.

“But somewhere along the way we seem to have thrown that all aside and we’ve chosen impunity, indifference, game show gambling over solidarity and humanity.”