U.S. President Donald Trump on Thursday threatened to destroy Iran's bridges and power plants, saying the "New Regime leadership knows what has to be done, and has to be done, FAST!" in a Truth Social post.

Trump did not elaborate on what needed to be "done," but said the U.S. "hasn't even started destroying what's left in Iran."

Hours later, Iran's semi-official Tasnim news agency reportedly claimed that a U.S. F-35 fighter jet was shot down over central Iran. Images of the jet were posted on Telegram, with one photo that appeared to show the words "U.S. Air Forces in Europe" on what appeared to be the tail section of a plane.

The U.S. Central Command, which oversees the region, and Iranian authorities did not respond to a request for comment at the time of publication.

Trump's latest threat came a day after a nationwide address in which he said the U.S. military would hit Iran "extremely hard" for the next two or three weeks. He added that the U.S. would "bring them back to the Stone Ages where they belong."

Hours after his speech, Iranian Foreign Minister Abbas Araghchi struck a defiant tone on X, saying that "there was no oil or gas being pumped in the Middle East back then," referring to Trump's stone age remarks.

"Are POTUS and Americans who put him in office sure that they want to turn back the clock?" Araghchi said.

Iran has effectively shut tanker traffic through the Strait of Hormuz, a vital global oil route, after the U.S. and Israel attacked the country on Feb. 28.

Trump has repeatedly threatened to send Iran back to the "stone age" as the war entered its second month and the U.S. military build-up in the Middle East showed no signs of slowing.

Despite reports of overtures from the U.S., including ceasefires and a 15-point peace plan to end the war, Iran has publicly contradicted multiple reports about negotiations with the Trump administration on numerous occasions.

Tehran had described the 15-point proposal as "extremely maximalist and unreasonable," according to an Al Jazeera report on March 25, citing a high-ranking diplomatic source.

Trump said Wednesday that Iran's "New Regime President" had asked Washington for a ceasefire, a claim that Tehran has denied. Trump has not specified who the "President" is.

"We will consider when Hormuz Strait is open, free, and clear. Until then, we are blasting Iran into oblivion or, as they say, back to the Stone Ages!!!," he wrote.

Attacks on power plants could constitute a war crime and violate international law, legal experts said.

In a letter dated Thursday and signed by over 100 law experts, the group said international law prohibits attacks on "objects indispensable to the survival of civilians, and the attacks threatened by Trump, if implemented, could entail war crimes."

Trump had also earlier said that he could target water desalination plants in Iran.

The Gulf Cooperation Council on Thursday called on the United Nations Security Council to take "all necessary measures to ensure the immediate cessation of Iranian aggressions against the Council states."

The six countries in the Gulf Cooperation Council — Bahrain, Kuwait, Oman, Qatar, Saudi Arabia and the United Arab Emirates — have come under attack from Iranian missiles and drones as the war entered its second month.

The Kuwait Petroleum Corporation said that its Mina al-Ahmadi refinery was hit by drones early on Friday.

Jassim Albudaiwi, Secretary-General of the Gulf Cooperation Council, said that while the bloc does not seek war, Iran had "exceeded all red lines" and described Tehran's attacks as "treacherous."

Bahrain, the current rotating president of the Security Council, has led an effort to pass a U.N. resolution to ​authorize "all necessary means" to protect commercial shipping in and around the Strait of Hormuz.

But the proposal reportedly stalled after veto-wielding Security Council members China, Russia and France objected to the draft resolution, which would have authorized military action against Iran.