The US has started bombing Iran once again after Donald Trump vowed to exact revenge.
Centcom confirmed strikes were underway late on Tuesday - which were made in "proportional response to unjustified Iranian aggression" after a US Army Apache helicopter was downed by Tehran.
Both crew members were rescued by a drone boat and are in a stable condition.
Mr Trump said earlier the US "must, of necessity, respond" to the downing of the helicopter as it was "patrolling over the Strait of Hormuz".
An investigation determined Iranian drones hit the helicopter and caused it to crash, but it remains unclear if the downing was intentional.
US officials told Axios it was targeting several Iranian air defence and radar systems near the Strait of Hormuz.
The President told US outlet ABC News the strikes would be "very powerful", as Iranian state media reported explosions at locations around the strait.
Iranian sources told the New York Times targets included naval bases in Sirik and Jask, air defenses in Bandar Abbas, and missile batteries in Qeshm.
Donald Trump said the US 'must, of necessity, respond' to the downing of the helicopter earlier in the Strait of Hormuz earlier today
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In the early hours of Wednesday, a second wave of explosions were heard in several cities near the strait.
State-linked media said "several consecutive explosions" were heard in Bandar Abbas, a port city to the north of the waterway.
Then, a third wave - with Qeshm Island, the strategic Iranian fortress in the strait under fire from "projectiles" launched from fighter jets.
The Iranian state-run Tasnim news agency said Tehran was plotting a "decisive response" to the attacks, and said the allegation it downed the Apache helicopter was a pretense.
Responding to the strikes, Iranian Foreign Minister Abbas Araghchi threatened to fire back and warned those in the region to evacuate.
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In a statement on social media, he said: "Despite its defeats on the battlefield, the US opted to test our determination.
"Our powerful armed forces will leave no attack or threat unanswered.
"Leave our region if you want to be safe. The history of the Persian Gulf has many chapters on dire fates of intruding outsiders."
Iran's Revolutionary Guards then claimed to have attacked the US Fifth Fleet in Bahrain with drones.
Iranian state media had said the situation on the ground had turned to "calm" after the first wave of strikes.
Before the strikes, Mr Trump - in a phone interview - told The Wall Street Journal the downing of the helicopter "wasn't a big deal", noting the pilot was "fine".
Iranian Foreign Minister Abbas Araghchi said 'Our Powerful Armed Forces will leave no attack or threat unanswered' in response to the latest US strikes
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While JD Vance earlier told CBS News a deal with Iran would "absolutely" be made before the US midterm elections in November.
Iran was "very close" to reaching a peace agreement which would address Iran's nuclear programme "for the long term", but an exact timeline was still unclear.
"I think we’re going to know a lot before the midterm elections," he said. "Look, I think that the deal could happen in the next week, but the deal could also happen months from now."
Mr Araghchi said earlier on Tuesday that foreign forces within Iranian territory were at "constant risk" of "their own human errors, plain accidents, or potentially being caught in crossfire".
"We prefer the language of diplomacy but speak other languages too," he warned.