US President Donald Trump said on Monday that the latest American strikes had hit Iran "very hard", describing the attacks as being carried out "in honour" of three US service members killed in recent days—two in Jordan and one in Iraq.
The remarks came as US Central Command (CENTCOM) said it had launched a "new wave" of strikes on Iran for a ninth consecutive night, with explosions reported across several parts of the country.
CENTCOM said the attacks targeted military sites and communications networks to further degrade Iran's ability to attack commercial shipping in the Strait of Hormuz.
Iran said it had retaliated with what it described as a "surprise attack" in Syria and had also targeted US aircraft at Jordan's Aqaba Airport.
Elsewhere in the region, Kuwait's armed forces said they had intercepted Iranian drones.
Iran's semi-official Tasnim news agency reported that US strikes hit several cities, including Tabriz, Chabahar, Konarak, Bandar Mahshahr and Bandar Imam Khomeini.
Iranian state media also reported that two oil tankers had exploded while attempting to transit the Strait of Hormuz.
The Islamic Revolutionary Guard Corps (IRGC) claimed the vessels had been using what it described as an "unsafe and hazardous southern route" through the strait and were "brought to a halt" after the explosions. CENTCOM disputed the claim.
The IRGC warned that the Strait of Hormuz would remain unsafe for the transit of petrochemical products and "even a single drop of oil and gas" as long as US strikes continued, adding that it would launch a "punitive operation" in response.
Over the weekend, the United States confirmed that one service member had been killed in an Iranian attack in northern Iraq on Saturday.
The death followed an attack a day earlier on a US base in Jordan that killed two American soldiers, while another service member remains missing. US officials said unidentified human remains had been recovered and were undergoing forensic identification.
As the exchange of strikes continued, US Secretary of State Marco Rubio said Washington remained open to diplomacy.
"The United States always remains open to a diplomatic solution," Rubio said.
He added that "the world has to decide whether or not it's going to allow an international waterway to be under the control" of Iran, accusing Tehran of using the Strait of Hormuz as leverage.
The latest escalation comes after a preliminary ceasefire agreed in mid-June collapsed. Efforts to negotiate a lasting peace have made little progress since Trump declared the agreement "over" on 8 July.