Iran's President Masoud Pezeshkian warned Saturday of a "more devastating" retaliation should Israel's nine-day bombing campaign continue, saying the Islamic republic would not halt its nuclear programme "under any circumstances".

Israel said on Saturday it had killed three more Iranian commanders in its unprecedented offensive, and Foreign Minister Gideon Saar claimed Tehran's alleged progress towards a nuclear weapon had been set back by two years.

"We will do everything that we can do there in order to remove this threat," Saar told the German newspaper Bild, adding that Israel would keep up its onslaught.

Israel and Iran have traded wave after wave of devastating strikes since Israel launched its aerial campaign on June 13, saying Tehran was on the verge of developing a nuclear weapon.

On Saturday, Israel said it had attacked Iran's Isfahan nuclear site for a second time, with the UN nuclear watchdog reporting that a centrifuge manufacturing workshop had been hit.

Later Saturday Iran's Mehr news agency said Israel had launched strikes on the southern city of Shiraz, which hosts military bases.

And early Sunday, Iran's Revolutionary Guard announced that a "vast" wave of "suicide drones" had been launched against "strategic targets" across Israel.

Iran denies seeking an atomic bomb, and on Saturday Pezeshkian said its right to pursue a civilian nuclear programme "cannot be taken away... by threats or war".

- 'Not prepared to negotiate' -

In a phone call with French President Emmanuel Macron, Pezeshkian said Iran was "ready to discuss and cooperate to build confidence in the field of peaceful nuclear activities".

"However, we do not agree to reduce nuclear activities to zero under any circumstances," he added, according to Iran's official IRNA news agency.

Referring to the Israeli attacks, he said: "Our response to the continued aggression of the Zionist regime will be more devastating."

Iran's armed forces threatened to strike shipments of military aid to Israel "from any country".

Israel's main arms supplier is the United States, whose President Donald Trump warned on Friday that Tehran had a "maximum" of two weeks to avoid possible American air strikes as Washington weighed whether to join Israel's campaign.

Iranian Foreign Minister Abbas Araghchi was in Istanbul on Saturday for a meeting of the Organisation of Islamic Cooperation to discuss the conflict.

Top diplomats from Britain, France and Germany met Araghchi in Geneva on Friday and urged him to resume nuclear talks with the United States that had been derailed by the war.

But Araghchi said Saturday: "Iran is ready to consider diplomacy once again, and once aggression is stopped and the aggressor is held accountable for the crimes committed."

"We're not prepared to negotiate with them (the Americans) anymore, as long as the aggression continues".

Trump, dismissive of European diplomatic efforts, said he was unlikely to ask Israel to stop its attacks to get Iran back to the table.

"If somebody's winning, it's a little bit harder to do," he said of Israel's campaign.

Any US involvement would likely feature powerful bunker-busting bombs that no other country possesses to destroy an underground uranium enrichment facility in Fordo.

US B-2 stealth bombers capable of carrying bunker busters were flying across the Pacific Ocean, according to tracking data and media reports, fuelling speculation over their intended mission.

Iran's Huthi allies in Yemen on Saturday threatened to resume their attacks on US vessels in the Red Sea if Washington joined the war, despite a recent ceasefire agreement.

The US-based Human Rights Activists News Agency said Friday that, based on its sources and media reports, at least 657 people had been killed in Iran, including 263 civilians.

Iran's health ministry on Saturday gave a toll of more than 400 people killed and 3,056 in the Israeli strikes.

Iran's retaliatory strikes have killed at least 25 people in Israel, according to official figures.

The Israeli military said it had launched a fresh wave of strikes Saturday in the area of southern Iran's Bandar Abbas, targeting drone storage sites and a weapons facility.

Iran's Tasnim news agency said air defences were activated in the area.

Overnight, Iran said it had targeted central Israel with drones and missiles. Israeli rescuers said there were no casualties after an Iranian drone struck a residential building.

Revolutionary Guards spokesman Mohammad Ali Naini said Iran's armed forces had "hit 14 strategic military" targets in the overnight attack, including Haifa's Sail Tower, the city's oil refinery and the Ovda airbase.

On the Mediterranean island of Cyprus, Israel said Saturday that an Iranian terror plot targeting Israeli citizens had been "thwarted".

- 'Tired' -

Israel's National Public Diplomacy Directorate said more than 450 missiles had been fired at the country so far, along with about 400 drones.

In Tel Aviv, where residents have faced regular Iranian strikes for nine days, some expressed growing fatigue under the constant threat from Iran.

The streets of Tehran, meanwhile, were still largely quiet Saturday, though a few cafes and restaurants were open.

In the afternoon, supporters of the government gathered briefly in front of the headquarters of state television to wave Iranian, Palestinian and Hezbollah flags to a soundtrack of electronic music whose lyrics called for the "death of Israel".

Western powers have repeatedly expressed concerns about the expansion of Iran's nuclear programme, questioning in particular the country's accelerated uranium enrichment.

International Atomic Energy Agency chief Rafael Grossi has said Iran is the only country without nuclear weapons to enrich uranium to 60 percent.

However, his agency had "no indication" of the existence of a "systematic programme" in Iran to produce a bomb.

Grossi told CNN it would be "pure speculation" to guess at how long it would take Iran to develop one.