In response, Iran's Islamic Revolutionary Guard Corps (IRGC) said it launched strikes on 21 targets at US bases in the region, one in Bahrain and the other in Jordan, while Kuwait's army said it was also intercepting an attack.
The US has described its strikes as "a proportional response" for the Apache helicopter downing on Monday, while the IRGC described the attacks as "vicious".
US President Donald Trump had earlier accused Iran of shooting down the helicopter and said the US "must, of necessity" respond. The two crew members survived and were rescued by an American sea drone.