The US military also confirmed a third death in recent days, saying a service member was killed on Saturday in northern Iraq, where the US has military bases, during a controlled detonation of what Central Command called unexploded ordnance on a downed Iranian attack drone.
Israeli authorities warned Iran that missiles launched toward Jordan could cause fire to spill over into Israeli territory for the first time in weeks.
The Israeli military said it had detected missiles fired from Iran toward the Jordanian port city of Aqaba, which lies just over Israel's southern border.
It alerted Israelis to expect air-raid sirens, the first in weeks.
The US and Iran have intensified attacks as an interim ceasefire deal signed a month ago has unravelled and a struggle for control of the Strait of Hormuz has deepened, raising the risk of a return to all-out hostilities.
Israeli officials said Israel was preparing to receive more US refuelling aircraft after the recent escalation, and ahead of a possible expansion of US military operations against Iran.
US Central Command said the latest air strikes, beginning at 6pm on Saturday, were designed "to further degrade Iran's ability to threaten commercial shipping in the Strait of Hormuz and swiftly punish Islamic Revolutionary Guard Corps forces who launched attacks against American service members in Jordan."
Central Command later said it had completed its wave of attacks, hitting Iranian military coastal surveillance and air defence facilities.
The conflict, which began when the US and Israel launched strikes on Iran on February 28 hoping to disable its nuclear and missile programs and degrade its regional proxies, has led to major disruption to energy supplies and fears over global inflation.
Iranian reports said the US carried out an attack near Sirik in southern Iran, and near Shadegan, close to the border with Iraq.
Iran's Atomic Energy Organisation condemned a US attack on the site of a nuclear power plant under construction in Darkhovin, Iran's Mehr news agency reported.
The International Atomic Energy Agency said it was investigating reports of an overnight attack, noting that the plant was in the very early stages of construction.
In response to the latest strikes, Iran carried out a drone attack that targeted US military sites and equipment at Kuwait's al-Adiri camp and Ali al-Salem Air Base, Iranian state TV reported early on Sunday.
Both bases have been targeted as part of Iran's attacks against US bases and allies in the Gulf since last week.
Kuwait's electricity ministry said a desalination plant had been attacked for the second day running, causing a fire.
Kuwait's armed forces said earlier they had again intercepted Iranian missiles, after a sustained Iranian attack on Saturday.
Bahrain's air defences also intercepted an Iranian attack on Sunday, its state TV reported.
Sirens sounded in Jordan, where the military said it had shot down three Iranian missiles.
In recent days both sides have taken aim at shipping traffic, with the US saying it is enforcing a naval blockade on Iran and Iran saying it targets vessels violating its rules on navigating the Strait of Hormuz, which usually handles one-fifth of global oil supply.
Iran's Islamic Revolutionary Guard Corps said on Sunday four vessels had attempted to transit the strait via an "unsafe route" with US backing after ignoring IRGC warnings.
It said two had abandoned the attempt while the other two were involved in an "accident".
Central Command said the earlier deaths of two of its service personnel had occurred on Friday.
The announcement brought the number of US service members killed since the war began to 16, while more than 420 have been wounded.
Iran's health ministry said 50 people had been killed and more than 500 wounded in US strikes over the past three weeks alone.
Overall, thousands have been killed and several million internally displaced in the conflict, mainly in Iran and in Lebanon, where a war between Israel and Iran-aligned militant group Hezbollah was reignited.
with AP and DPA
