Iran’s supreme leader has warned of “unforgettable lessons” if the United States keeps attacking the Islamic Republic and called President Donald Trump’s signature “worthless and invalid.”

The comments came hours after a negotiator said Iran was suspending its commitments to the interim deal signed about a month ago.

The statement attributed to Mojtaba Khamenei, still unseen since the war began, was read out on state television after the United States and Iran again exchanged strikes aimed at infrastructure and military targets.

Iran Supreme Leader Mojtaba Khamenei hasn’t been seen since war began. Photo: EPA

Iran’s declarations snapped another fragile thread as the war shows no end in sight. The deal was aimed at permanently ending the fighting. Now Khamenei warns of “lessons” not only from Iran but its armed proxies in the region, calling them the “Axis of Resistance”.

The battle over the Strait of Hormuz has intensified in a conflict increasingly focused on control of the essential waterway that previously carried a fifth of the world’s crude oil. The widening strikes threatened civilians and services to them, including desalination plants for drinking water, while the global economy again was on alert.

The US Central Command said early on Saturday that its seventh straight night of strikes hit “surveillance sites, military logistics infrastructure, underground weapons storage, and maritime capabilities”.

The US has violated its commitments under the deal that was signed about a month ago and now Iran is “no longer implementing them,” Kazem Gharibabadi, Iran’s deputy foreign minister, told state TV.

President Donald Trump’s signature is worthless, says Iran’s supreme leader. Photo: AP

The most significant damage from Iranian strikes on Saturday occurred in Kuwait, where a water desalination plant and an oil facility were hit, according to the Kuwait authorities and the Kuwait Petroleum Corporation. Both declined to provide locations.

The strikes injured several people at the oil facility and caused a fire at the desalination plant, forcing several power generation units offline. It was the second attack against a desalination plant in two days in the tiny desert nation that depends on desalination for 90 per cent of its drinking water.

Several firefighters and a worker were injured while battling two other blazes sparked by Iranian strikes, according to the Kuwait Fire Force. Kuwait briefly closed its airspace due to missile threats, and Kuwait Airways said it was rescheduling most flights to and from the capital.

Meanwhile, Iraq said it shot down attack drones over the city of Irbil. Jordan’s state-run Petra news agency said the kingdom’s air defence systems had downed Iranian missiles, while air sirens sounded multiple times in Bahrain throughout the day and in Saudi Arabia in the morning, according to their governments.

The secretary general of the six-nation Gulf Cooperation Council, Jasem Mohamed al-Budaiwi, accused Iran of war crimes for strikes on infrastructure and civilian facilities.

US air strikes hit an electricity and desalination plant in Iran’s southern Hormozgan province, Iranian state TV reported. IRNA said the Bonji desalination plant was destroyed, cutting off water supplies to about 10,000 people, and that a desalination plant on strategic Qeshm Island inside the strait was damaged.

The battle over the Strait of Hormuz has intensified in a conflict increasingly focused on control. Photo: AP

Overnight strikes damaged two tunnels and a bridge, disrupting one of the main highways toward Bandar Abbas, Iran’s main port that sits near the narrowest part of the strait, according to Iran’s state-run news agency. IRNA said three bridges were hit Saturday, including one on a route to Bandar Abbas.

Iran acknowledged “attacks on power infrastructure” during the US air strikes for the first time on Friday when its Energy Ministry issued a call for people to use less power in southern provinces “experiencing extreme heat.” It did not specify what was hit.

The Islamic Revolutionary Guard Corps stepped up its warning that countries hosting US forces should be “prepared to receive a corresponding response,” according to Iran’s state TV.

Iranian authorities said at least 50 people have been killed and more than 500 wounded in US strikes in the past three weeks, including eight killed in a strike on a bridge Friday.