A US base and a power station were also targeted, in what was the most dramatic escalation for the small Gulf country in decades, after the 2003 US invasion of Iraq and Baghdad's attempt to take over Kuwait in 1990.

Blasts also rang out over the Gulf cities of Abu Dhabi, Dubai, Doha and Manama as Iran targets the United States' Gulf allies after the killing of its supreme leader in US-Israeli strikes.

The embassy in Kuwait did not announce it had been hit but issued a security alert urging people to stay away.

"There is a continuing threat of missile and UAV (drone) attacks over Kuwait. Do not come to the embassy," the statement said, adding: "US embassy personnel are sheltering in place."

The Iranian attacks have so far killed five people in the Gulf, according to authorities, including one person in Kuwait.

The small, oil-rich country has a large US military presence stemming from the 1990 Iraqi invasion, which was repelled by a US-led coalition aiding the Kuwaiti army.

Three F-15E Strike Eagles were mistakenly shot down by Kuwait air defences late on Sunday night, the US Central Command said.

"During active combat -- that included attacks from Iranian aircraft, ballistic missiles, and drones -- the U.S. Air Force fighter jets were mistakenly shot down by Kuwaiti air defenses," CENTCOM said Monday, adding that all six aircrew ejected and were safe.

"Kuwait has acknowledged this incident, and we are grateful for the efforts of the Kuwaiti defense forces and their support in this ongoing operation," it added.

- Worried residents -

In northern Kuwait, smoke billowed over a power station, three witnesses told AFP.

An energy ministry spokeswoman said a fuel container at the station had been hit by shrapnel as air defences were intercepting drones, causing a limited blaze.

Separately, Iran's army said it targeted the Ali Al Salem air base hosting US troops in Kuwait, as well as vessels in the Indian Ocean, firing 15 cruise missiles.

Also on Monday, shrapnel fell at Mina Al Ahmadi refinery, one of Kuwait's biggest, injuring two workers, but did not disrupt production, the Kuwait National Petroleum Company said.

Sirens sounded over Kuwait City on Monday to warn of incoming strikes. An unspecified number of drones was intercepted at dawn, the interior ministry said.

Dana Abbas, a Kuwait City resident and engineer, said she was worried about the escalation and had rushed to fill her car with petrol and stock up on basic necessities.

On Sunday, the UAE said fallen debris hit the facade of Etihad Towers, which houses diplomatic embassies including Israel's, causing minor injuries to a woman and a child.

Iran's unprecedented bombardment has hit military bases but also civilian infrastructure such as residential buildings, hotels, airports and sea ports, rattling a region long seen as a refuge from Middle East conflict.