President Donald Trump said the US “hasn't even started destroying what's left in Iran", reiterating vows to increase the ferocity of attacks on its infrastructure, as the war neared the end of its fifth week unabated and the UN Security Council prepared to meet over Tehran's stranglehold on the Strait of Hormuz.

The war in Iran continues to spread chaos across the region and roil financial markets, raising the pressure on Trump to find a quick resolution to the conflict.

Trump has stepped up his rhetoric in recent days as negotiations conducted via intermediaries with new leaders in Iran show limited signs of progress and pessimism at home about the war grows.

The US military "hasn't even started destroying what's left in Iran. Bridges next, then Electric Power Plants," Trump wrote on social media late on Thursday, adding that Iran's leadership "knows what has to be done, and has to be done, FAST!"

He earlier posted a video of the US bombing a newly constructed bridge between Tehran and nearby Karaj. The B1 bridge was scheduled to open to traffic this year. According to Iran's state media, eight people were killed and 95 others were wounded in the US attack.

"Striking civilian structures, including unfinished bridges, will not compel Iranians to surrender," Iran foreign minister Abbas Araghchi said in a statement.

Satellite images also showed smoke rising from the port in Qeshm, an Iranian island strategically located in the Strait of Hormuz, earlier this week.

Iran fires back, Israel, US hit Tehran

Iran fired on targets across the Middle East, sparking multiple blazes at a Kuwaiti oil refinery, while American and Israeli airstrikes hit the Islamic Republic early Friday.

Despite claims from the US and Israel that Iran's military capabilities have been all but destroyed, Tehran has continued to keep the pressure on Israel and its Gulf Arab neighbours, hitting Kuwait's Mina al-Ahmadi oil refinery early Friday in a drone attack.

The refinery has been hit multiple times during the war, and state-run Kuwait Petroleum Corp. said firefighters were working to control several blazes. Sirens also sounded in Bahrain, warning of Iranian attacks, and Israel reported incoming missiles.

Activists reported strikes around Tehran and the central city of Isfahan, but it wasn't immediately clear what was hit.

Iran's attacks on Gulf region energy infrastructure and its tight grip on the Strait of Hormuz, through which a fifth of the world's oil and natural gas transits in peacetime, have sent oil prices skyrocketing and are impacting global economies.

Spot prices of Brent crude, the international standard, were around $109 early Friday, up more than 50 per cent from February 28 when Israel and the US started the war with their attacks on Iran.

Hormuz question in UN Security Council

The UN Security Council was expected to vote Saturday on a proposal from Bahrain that would authorise defensive action to ensure vessels can safely transit the strait. Bahrain's initial draft would have allowed countries to "use all necessary means" to secure the strait, but Russia, China and France – who have veto power on the Council – expressed opposition to approving the use of force.

Speaking Thursday in South Korea, French President Emmanuel Macron said the American expectation that the Strait of Hormuz could be reopened by force was unrealistic.

Macron said a military operation "would take an infinite amount of time and would expose anyone passing through the strait to coastal threats from (Iran's) Revolutionary Guard." He added that reopening of the strait "can only be done in coordination with Iran," through negotiations that would follow a potential ceasefire.

Talks organised by Britain and involving more than 40 countries focused on political rather than military means to secure the strait. The nations, which didn't include the US, urged increased diplomatic pressure on Iran and possible sanctions.