The United States and Israel launched strikes on hundreds of targets across Iran on Monday, and Israel expanded its bombing campaign to Lebanon as defiant Iranian forces continued firing missiles and drones across the Middle East in retaliation for the deaths of Iran's Supreme Leader Ayatollah Ali Khamenei and as many as 40 senior officials.

Iran's surviving leaders said the counterattacks were justified as self-defense. Ali Larijani, the secretary of Iran's National Security Council, flatly refuted on Monday media claims that he had made a fresh push to resume nuclear talks with Washington, stressing Tehran's refusal to engage in any negotiations amid the ongoing hostilities.

The Israeli military said it is striking at the heart of Tehran and has launched attacks on Lebanon after Hezbollah fired a barrage of rockets at northern Israel. Lebanon's Health Ministry said more than 30 people have been killed and 150 wounded in the Israeli attacks.

Fresh explosions were heard across the Gulf on Monday, including in the cities of Dubai, Doha and Manama. Civilian infrastructure has been targeted, ranging from airports and seaports to residential buildings and hotels.

"The Gulf countries right now are really on the front lines of this war. As always, the Gulf states want to support de-escalation and diplomacy ... But this commitment and these principles are being put to the test right now," Anna Jacobs, a security analyst, said.

Nasdaq Dubai will be temporarily closed for two days, market regulator Dubai Financial Services Authority said on Monday.

Trump, speaking to The New York Times, said the US and Israel could keep up the level of attacks for four to five weeks.

"It won't be difficult. We have tremendous amounts of ammunition," he said, adding he had a shortlist of three unnamed people he favored to lead post-war Iran.

British Prime Minister Keir Starmer said on Sunday that he would let the US use UK bases for "defensive" strikes but that his country -- a steadfast partner in the US-led wars in Iraq and Afghanistan -- "will not join offensive action now". Earlier, the British airbase in Cyprus was targeted by Iranian drones, causing "limited" damage.

The Pentagon said three US service members were killed in the operation "Epic Fury".

Trump, who campaigned on a platform of denouncing foreign interventions, has done little to explain the case for war to the US public.

Hakeem Jeffries, the top Democrat in the House of Representatives, said the soldiers' deaths were the result of a "reckless decision" and that there was no threat to "justify this type of preemptive military strikes".

Three ships were also attacked in the Strait of Hormuz on Sunday after Iran declared the closure of the strategic waterway, sending global oil prices spiking. Container shipping company Maersk said it was halting passage through the Suez Canal and the Strait of Hormuz for "safety" reasons.

Iran's Revolutionary Guards claimed to have struck the aircraft carrier USS Abraham Lincoln with four missiles, but the Pentagon said the "missiles didn't even come close".

On Sunday, members of the Gulf Cooperation Council condemned Iranian attacks on their territories. In a joint statement, foreign ministers and senior officials from the United Arab Emirates, Saudi Arabia, Bahrain, Qatar, Kuwait and Oman stressed their "legal right to respond ... the right of self-defence, individually and collectively, in the event of aggression".

The UAE said on Sunday it was closing its embassy in Tehran and recalling the ambassador, marking the strongest condemnation yet by a Gulf state in the ongoing conflict.

Since Saturday, the UAE has detected 165 ballistic missiles, destroying 152, and intercepted two cruise missiles, the military said, adding that 506 of 541 Iranian drones were shot down.

Tehran also appeared to target a building complex on Sunday in the UAE capital Abu Dhabi that houses the Israeli embassy.