Kuwaiti air defences were intercepting missile and drone attacks of undisclosed origin, state media reported, while in Bahrain sirens sounded and residents were urged to seek shelter after US and Iran exchanged fire.
US forces struck Iranian coastal radar sites on Saturday after shooting down drones launched by Iran toward the Strait of Hormuz.
US Central Command said on X that the US then struck Iran's surveillance sites in Goruk and Qeshm Island, which are both on the Strait of Hormuz.
The US military believes the four Iranian drones were targeting regional maritime traffic, a US official told Reuters.
Iran’s Revolutionary Guard Corps said it had targeted US bases in the region with missiles in retaliation for US strikes and fired on four tankers attempting to cross the strait without its permission.
Iran said it had hit US bases in Kuwait and Bahrain with ballistic missiles but the US military said six missiles were intercepted and a seventh did not reach its target.
The US and Iran have been engaged in largely indirect negotiations to secure an interim deal to halt the three-month-old war that would leave issues including Iran's nuclear programme to further negotiations.
But amid periodic skirmishes a deal has remained elusive.
As part of any agreement, Tehran wants access to billions of dollars in oil revenue, waivers on sanctions on crude exports, the lifting of a US blockade on its ports and leverage over the strait. Iran has effectively blocked the strait, where about a fifth of the world's oil transited before the war.
US President Donald Trump is facing mounting domestic political pressure due to rising gas prices to bring the unpopular war to an end. He told NBC that while most of Iran's drone and missile manufacturing facilities had been destroyed, the Iranians still have access to about a fifth of their missiles.
"They have some missiles, they have some drones. I would say percentage wise, maybe 21 per cent-22 per cent of their missiles. It's a lot of missiles, but it's not what it was when we first attacked," Trump told NBC News' "Meet the Press" programme, according to excerpts released by the network on Friday.
When asked why Iran’s leaders — if as desperate as he has portrayed them — were not more inclined to strike a deal, Trump said: "Because they are strong. They're proud. There are things they never thought they'd be doing that they're going to have to do, they've got no choice, and it takes a little while."
After the US and Israel launched the war against Iran on February 28, Tehran fired missiles and drones against Gulf states hosting US bases and largely stopped shipping through the Strait of Hormuz.
The conflict has driven up oil prices and disrupted supply chains for other products. The UN World Food Programme said on Friday that it was pushing millions of people closer to hunger due to rising fuel and transport costs.
Mohsen Rezaei, an adviser to Iran's supreme leader, told CNN on Friday that a peace deal hinged on the Trump administration unfreezing $24 billion in Iranian assets, and warned that the US would "enter into a dark corridor" if it resumed attacks.
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