Kuwait came under sustaine d attack on Saturday, with a desalination plant hit and operations at Kuwait International Airport suspended due to repeated missile and drone threats.
Iran's Revolutionary Guards said they struck a US military support centre at Camp Arifjan and destroyed a radar facility at Ali Al Salem Air Base in Kuwait.
Iranian state media reported that in Bahrain, the Revolutionary Guards targeted a site where US combat aircraft were gathered at Sheikh Isa Air Base and an intelligence data centre.
Reuters was not able to verify the reports.
"Since there is no international institution to prevent the savagery of the US military, we have no path before us except the Quranic command: 'Whoever attacks you, attack it in the same manner'," the Guards said in a statement warning US allies in the region to expect more strikes.
On Friday, both sides took aim at shipping traffic, with the US saying it was enforcing a naval blockade while Iran said it targeted vessels that violated its rules on navigating the Strait of Hormuz, the vital waterway for one-fifth of the world's oil supply.
Oil prices climbed more than four per cent on Friday to their highest level in more than a month, applying political pressure on US President Donald Trump as his Republican Party tries to hold on to power in November congressional elections.
Washington and Tehran have been testing the limits of escalation since their ceasefire agreement collapsed on July 7, raising the prospect of a return to all-out war.
Civilian infrastructure was increasingly being subjected to attack despite concerns about potential war crimes.
Iranian media reported that several missiles struck power facilities and desalination pumps in the southern city of Jask on Saturday, citing a local official.
Some 10,000 people in 20 villages were without water, Tasnim news agency reported.
A power generation and water desalination plant in Kuwait was hit in an Iranian attack, the country's electricity, water and renewable energy ministry said in a statement.
It was the second attack on Kuwaiti water desalination sites in two days.
The US military's Central Command earlier said it concluded its seventh consecutive day of strikes by hitting Iranian surveillance sites, military logistics infrastructure, underground weapons storage and maritime capabilities.
UN Secretary-General Antonio Guterres was concerned about escalation in the conflict, particularly "attacks on civilian infrastructure in Iran and across the region", his spokesperson said on Friday.
Iranian media reported strikes early on Saturday in Hormozgan Province on the Strait of Hormuz.
State TV said three people were killed and eight wounded while two bridges and a road tunnel were damaged.
A day earlier, Iranian state media said US strikes hit at least five bridges in the south.
Seven people were reported killed in attacks on bridges in the southern port of Bandar Khamir, where a train station was also hit.
An airport was reported hit further east in Iranshahr.
Trump has threatened to launch broad-based air strikes on Iran's infrastructure and has also declined to rule out a ground assault on Iran's coast or islands.
US officials have said attacks on southern Iran are designed in part to give Trump options.
Such moves risk provoking Iran to attack the vital infrastructure of vulnerable Gulf states, or having its allies in Yemen further disrupt global energy supplies by attacking shipping from the Red Sea.
