The international benchmark Brent crude jumped up by almost three percent after the US Central Command announced the new wave of bombings, and China urged both sides to respect their truce and resolve their dispute peacefully.

Iran did not immediately confirm the reported strikes, but state media reported blasts in the southern port city of Bandar Abbas, and the Revolutionary Guards Corps said its forces had downed a US drone entering its airspace and fired at an F-35 fighter jet.

In a statement marking the start of the Eid al-Adha holiday, Tehran's supreme leader Ayatollah Mojtaba Khamenei declared that Washington was losing its influence in the Middle East and warned countries in the region to stop hosting bases from which the US could launch attacks.

The United States, he said in a written statement, "in addition to no longer having any safe haven in the region for aggression and the establishment of military bases, is moving further and further away from its former position with each passing day".

Tim Hawkins, a spokesman for US Central Command, said: "US forces conducted self-defence strikes in southern Iran today to protect our troops from threats posed by Iranian forces."

- 'We'll see' -

He gave few details of the attacks and said only that the targets included missile launch sites and boats trying to "emplace mines."

Despite the strikes, Secretary of State Marco Rubio said on Tuesday that a deal remained within reach.

But he remained firm on the Strait of Hormuz, the key oil and gas shipping route out which Iran is seeking to control.

"There were some talks going on in Qatar today, so we'll see if we can make progress. I think it's a lot of talking back and forth going on about specific language in the initial document, so it'll take a few days," Rubio told reporters, during a visit to India.

He said the strait was "going to be open one way or the other," adding: "What's happening there is unlawful, it's illegal, it's unsustainable for the world, it's unacceptable."

A report by the Tasnim news agency said Tehran's negotiators are seeking the release of frozen assets, with half made available as soon as an inital memorandum of understanding is signed.

This came as a top Iranian delegation was in Qatar, and after Tehran said it was finalising a 14-point framework for a deal on ending the war, which began with US-Israeli airstrikes on February 28.

"Iran's frozen assets are to be released during the course of the negotiations, and this amount is estimated at $24 billion in accordance with the 14-point memorandum of understanding," Tasnim said, quoting what it said was an unnamed source close to the negotiating team.

- Frozen assets -

Iran's top negotiator, parliamentary speaker Mohammad Bagher Ghalibaf, arrived in Qatar on Monday for talks along with Foreign Minister Abbas Araghchi and Central Bank Governor Abdolnaser Hemmati.

Tasnim said Ghalibaf's trip was "aimed at reaching an understanding on the implementation of Iran's demand and the method of accessing $12 billion in the first phase".

In 2023, $6 billion in frozen Iranian funds held in South Korean banks was transferred to Qatar pending the release of five American citizens detained in Iran.

The new strikes threatened a ceasefire that began on April 8 as the United States and Iran struggle to reach an accord to end a war that has rattled the global economy with a severe disruption of energy flows.

China, Washington's great power rival and a major energy importer, expressed concern.

"We urge the parties concerned to fulfil their ceasefire commitments, resolve disputes through peaceful means... and promote the early restoration of peace," foreign ministry spokeswoman Mao Ning told reporters.

Hopes of an accord took another blow when Israeli Prime Minister Benjamin Netanyahu vowed to "crush" Hezbollah in Lebanon on Monday evening.

Iran has demanded that any peace accord apply to the fighting in Lebanon as well.

On Tuesday, Israel warned Lebanese civilians to evacuate the southern city of Nabatieh ahead of more planned strikes.

President Donald Trump said in a social media post that he expected Iran to hand over its enriched uranium to the US to be destroyed, or have it destroyed in Iran with an international witness.

The nuclear fuel "will either be immediately turned over to the United States to be brought home and destroyed or, preferably, in conjunction and coordination with the Islamic Republic of Iran, destroyed in place or, at another acceptable location".