The US has launched “self-defence strikes” against Iran after Donald Trump blamed Tehran for downing a US army helicopter near the strait of Hormuz, imperilling a shaky ceasefire that was announced by the two countries in April.

US Central Command said Trump had directed the military to launch strikes beginning at 10pm UK time on Tuesday in response to the downing of the Apache helicopter gunship off the coast of Oman earlier. US media, citing White House officials, have said Centcom is targeting radar and air defence facilities along the strait of Hormuz.

Trump had said in a post on his Truth Social platform that Iran was responsible for the crash, and that Washington could not allow such an event to go unanswered.

At the same time, US officials also signalled that they were not seeking a return to full-scale war with Iran. “The mission is a proportional response to unjustified Iranian aggression,” Centcom said. Tehran has not yet indicated whether it is planning its own retaliation.

The helicopter’s two crew members were later rescued in an unprecedented operation using an unmanned drone boat, the US military said.

Trump played down the incident in an interview with the Wall Street Journal, saying that the strike on the helicopter “wasn’t a big deal” and that the “pilot is fine”.

The helicopter went down as the Middle East was still reeling after Iran and Israel exchanged fire on Monday, in the biggest blow yet to the strained ceasefire. Iranian state television reported on Tuesday that the Israeli attacks killed at least two members of the country’s air defence units.

Since the US and Israel began striking Iran on 28 February the war has shaken the global economy, forced up energy prices around the world and made many basics, including food, more expensive.

Officials have been unable to turn the April ceasefire into a deal to permanently end the conflict, particularly as Israel intensifies and expands its military campaign in Lebanon against the Iranian-backed Hezbollah militia.

The crash happened at about 3.30am local time on Tuesday off the coast of Oman while the helicopter was on a patrol, US Central Command said.

An unmanned boat located the two aviators after they spent about two hours in the water, said Centcom spokesperson Capt Tim Hawkins. He said it was the first known drone rescue at sea by the US military.

Military officials did not say what caused the Apache helicopter to go down, saying the crash was under investigation. Trump said he had just learned Iran was responsible before posting his accusation on Tuesday.

AH-64 Apache helicopters have been a key asset for the American military as it enforces a blockade on Iranian crude oil shipments and tankers, seeking to put pressure on Tehran to make a deal. The helicopters have also been used by the United Arab Emirates to shoot down Iranian drones.

The drone used to perform the rescue was a 24ft (7.3-metre) vessel called a Corsair, Hawkins said.

Before Trump accused Iran of downing the US helicopter, he had expressed renewed optimism over negotiations with Iran, saying there was “a good chance” of signing a deal in “two or three days”. He did not provide any details on why there was reason for new optimism. In the two months since the US and Iran agreed to an initial ceasefire, Trump has repeatedly predicted a deal was near.

“We’re very close to having a very, very good, strong, powerful deal,” the president said. “If we go and bomb – which we could do very easily if we want, and we spend another two or three weeks bombing – they’ll have nothing left whatsoever. But you won’t have the strait open for months.”

He added: “If we do the bombing, you know, a lot of people are going to be killed. Who wants to do that? I don’t.”

Iran’s chief negotiator, Mohammad Bagher Ghalibaf, said: “We prefer the language of diplomacy, but we speak other languages far more fluently. Break your commitments, and we’ll switch to what we speak best.”

With reporting by the Associated Press