As the war between the longtime arch-rivals entered its 11th day despite international calls for de-escalation, here are the latest developments:

- 'Extension of war' -

Iran's armed forces threatened on Monday to inflict "serious, unpredictable consequences" on the United States in retaliation for its strikes on nuclear sites.

US warplanes unleashed bunker-buster bombs on Isfahan, Natanz and the underground uranium enrichment facility at Fordo, in support of the bombardment campaign ally Israel began on June 13.

"This hostile act... will widen the scope of legitimate targets of the armed forces of the Islamic Republic of Iran and pave the way for the extension of war in the region," said armed forces spokesman Ebrahim Zolfaghari on state television.

Ali Akbar Velayati, an adviser to Iran's supreme leader Ayatollah Ali Khamenei, said bases used by US forces "in the region or elsewhere" could be attacked.

The US State Department issued a "worldwide caution" for Americans on Sunday.

The leaders of Britain, France and Germany and called on Iran "not to take any further action that could destabilise the region".

At a UN Security Council emergency meeting Sunday, Secretary-General Antonio Guterres warned against "descending into a rathole of retaliation after retaliation".

- Trump claims 'monumental damage' -

Trump wrote on social media on Sunday that "Monumental Damage was done to all Nuclear sites in Iran, as shown by satellite images. Obliteration is an accurate term!" He did not share the images he was referencing.

US Joint Chiefs Chairman Dan Caine said seven B-2 stealth bombers had flown 18 hours to drop 14 GBU-57 bunker-buster bombs -- a powerful 13,600-kilo (30,000-pound) weapon.

US Defense Secretary Pete Hegseth said the strikes had "devastated the Iranian nuclear programme", but "did not target Iranian troops or the Iranian people".

The UN's International Atomic Energy Agency said it had not detected any increase in radiation levels at key nuclear sites in Iran after the US strikes.

- 'Regime change' -

While Hegseth said at a press briefing that "this mission was not... about regime change", Trump mulled the possibility.

"It's not politically correct to use the term, 'Regime Change,' but if the current Iranian Regime is unable to MAKE IRAN GREAT AGAIN, why wouldn't there be a Regime change???"

Iran "must now agree to end this war", Trump said after the strikes, insisting that under no circumstances should it possess a nuclear weapon.

Israeli Prime Minister Benjamin Netanyahu, who has not ruled out targeting Iran's clerical leadership, said "thanks to President Trump, we have moved closer to our goals".

- Strikes, missiles -

Sirens sounded in Israel and Iran early Monday as the arch enemies exchanged their latest round of fire.

The Israeli air force struck "military infrastructure sites in Kermanshah" in Iran's west, a military statement said, while Iranian news agency Fars reported a drone attack.

The Israeli army said it was intercepting missiles from Iran early Monday.

Tehran governor Mohammad Sadegh Motamedian told state TV that "more than 200 locations have been attacked" across the capital since the start of Israel's bombing campaign on June 13.

Israeli strikes on Iran have killed more than 400 people, Iran's health ministry said. Iran's attacks on Israel have killed 24 people, according to official figures.

- Iran execution -

Iran's judiciary said it executed on Monday a man found guilty of spying for Israel, the second such hanging in as many days.

Iran is the world's second-most prolific executioner after China, according to human rights groups including Amnesty International.

On Sunday, authorities pledged to speed up cases of individuals accused of working with foreign intelligence agencies, particularly its arch-foe Israel.

burs-ami/dv