Earlier the US military said it had shot down Iranian drones over the Strait of Hormuz and struck a military site in Bandar Abbas, a strategic port city.
The renewed hostilities threaten a fragile ceasefire between the US and Iran.
It is the second time in three days that the US has attacked targets in Iran - saying that the strikes were conducted in self defence.
The site in Bandar Abbas was struck as it was about to launch a fifth drone, US Central Command (Centcom) said. Iranian media reported that explosions were heard to the east of the city.
Centcom described its actions as "measured, purely defensive, and intended to maintain the ceasefire".
It also said its forces shot down four Iranian one-way attack drones "that posed a threat around the Strait of Hormuz".
Iran condemned the strikes as "a grave violation of the ceasefire" and vowed that the Iranian government "will not leave any act of hostility unanswered."
