Iran announced attacks on Gulf countries that host U.S. 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.
Iran said it had struck U.S. bases in Kuwait, Qatar and Bahrain, and a U.S. 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 U.S. special forces base in Tanf, which Damascus and Washington say U.S. 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 U.S. 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 U.S. 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.
Iran has 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 Iran has already instructed the Houthis to act if Washington attacks Iran's infrastructure.