At sea, where the renewed conflict has again cut off energy supplies from the Gulf, US Marines boarded a tanker near the Strait of Hormuz. Another vessel was seized by armed men off ‌Yemen, raising concern over security in the Middle East’s other big choke point for oil shipments at the mouth of the Red Sea.

Washington and Tehran have been testing the limits of escalation since their ceasefire agreement collapsed last week, raising the prospect of a return to all-out war.

As reports of Friday’s escalation emerged, benchmark Brent crude oil prices surged by more than 3% to near $87, the highest level since an interim agreement a month ago aimed at ending the war. Global share prices fell, with Wall Street opening sharply lower.

US President Donald Trump ​has threatened to launch broad-based air strikes on Iran’s infrastructure and has also declined to rule out a ground assault on Iran’s coast or islands. US officials have said attacks on southern Iran are designed in ​part to give Trump options.

Such moves risk provoking Iran to escalate in turn by hitting the vital infrastructure of vulnerable neighbouring Arab states, or having its allies in Yemen further ⁠disrupt global energy supplies by attacking shipping from the Red Sea.

BRIDGES HIT IN IRAN, PLANT HIT IN KUWAIT

In the latest strikes, the US military’s Central Command included “military logistics infrastructure” in the list of targets it said it had hit, the first ​time it has mentioned infrastructure in more than a week.

Iranian state media said at least five bridges had been struck in the south. Seven people were reported killed in attacks on bridges in the southern port of Bandar Khamir, where the ​train station was also hit. An airport was reported hit further east and away from the coast in Iranshahr, in a province bordering Pakistan.

Reuters was unable to confirm details of the reports, which also described other deadly attacks, including one which killed a woman and wounded her child in the port of Bandar Abbas.

In response, Iran announced attacks on Gulf countries that host US airbases, including Bahrain, Qatar and Kuwait.

Authorities in Kuwait said one of the country’s power generation and water desalination stations had been hit in an Iranian attack, causing damage to ​facilities, a fire and the disruption of a large number of electricity generation units.

Firefighters brought the blaze under control, while technical teams began assessing the damage, securing the station and working to restore power generation as soon as possible, ​the Ministry of Electricity, Water and Renewable Energy said.

The rich Arab Gulf states depend on plants that produce electricity and remove salt from seawater to make their desert cities habitable. When Iran hit a Kuwaiti desalination plant on March 30, it was seen as a ‌major escalation that ⁠helped push the United States to declare the war’s first ceasefire a week later.

FEUD OVER STRAIT

Iran said it had struck US bases in Kuwait, Qatar and Bahrain, and a US radar station in Oman. Explosions were heard in the Qatari capital, Doha, where the interior ministry said a child was wounded by shrapnel.

Iran also said it fired at Syria, apparently for the first time in the war, targeting what it described as a US special forces base in Tanf, which Damascus and Washington say US forces vacated earlier this year. A Syrian military source said the strike hit near the base and caused no damage or casualties. CENTCOM said no US troops were killed or captured.

Last month’s interim agreement to end the ​war has collapsed since July 7, when Iran struck ships ​in the Strait of Hormuz, and the United States ⁠responded with air strikes. Iran has since announced the closure of the strait, and Washington has reimposed its own blockade of Iranian ports.

In the latest action at sea, the US military said it had boarded a tanker to enforce the blockade, releasing photos of Marines rappelling down from a helicopter onto the deck where one posed in front of an ​Iranian flag.

Beyond the Gulf, armed assailants boarded and seized a small chemical tanker off Yemen in the Gulf of Aden, close to the mouth of the Red Sea.

One maritime security ​source said the incident appeared ⁠to be related to Somali piracy rather than action by Iran’s Yemeni allies, the Houthis. But security sources in the Horn of Africa have spoken in the past of concern about the potential for the Houthis to assist, encourage or arm pirates in the area.

While Iran and the United States have exchanged strikes daily since last week, they have so far stopped short of escalating beyond parameters set earlier in the war, when civilian infrastructure and major economic targets were mostly deemed out of bounds because ⁠of the threat ​of retaliation.

Iran has said that it would attack civilian infrastructure across the Middle East if Trump follows through on threats to attack Iran’s infrastructure.

It ​has also signalled that it could prod its Houthi allies in Yemen to close another key strait: the Bab al-Mandeb at the mouth of the Red Sea, potentially cutting off the main alternative route for Middle East oil bypassing the Gulf.

Sources have told Reuters that Iran has already instructed the Houthis ​to act if Washington attacks Iran’s infrastructure.