US President Donald Trump rejected a public address, but took to Twitter saying “all is well!” after Iran fired more than a dozen ballistic missiles targeting American troops in Iraq.

Mr Trump tweeted “so far, so good”, despite threats of Iranian terror attacks on American soil and a major lurch toward war between the US and Iran.

The missile strikes on two US military bases were the most dangerous development in the brewing conflict in the Middle East.

• To understand how the Iran-US crisis developed, click here.

While there were no immediate reports of US casualties, an Iraqi security source was quoted by CNN as reporting several Iraqi casualties at Ain al-Asad airbase following the attack.

The missiles were launched in retaliation for a US drone strike that killed Iran’s top commander in Baghdad last week, Iranian official news media said on Wednesday.

In a statement on its Telegram channel, Iran’s Islamic Revolutionary Guard Corps (IRGC) said: “The fierce revenge by the Revolutionary Guards has begun”.

Mr Trump said an assessment of casualties and the damage was underway.

“We have the most powerful and well equipped military anywhere in the world, by far!” he said.

He said he will make an official statement on Thursday morning (US time).

All is well! Missiles launched from Iran at two military bases located in Iraq. Assessment of casualties & damages taking place now. So far, so good! We have the most powerful and well equipped military anywhere in the world, by far! I will be making a statement tomorrow morning.

— Donald J. Trump (@realDonaldTrump) January 8, 2020

Iran’s foreign minister, Javad Zarif, said his country’s response to General Qassem Soleimani’s assassination was proportional, and that he did not want the situation to escalate.

Iran took & concluded proportionate measures in self-defense under Article 51 of UN Charter targeting base from which cowardly armed attack against our citizens & senior officials were launched.

We do not seek escalation or war, but will defend ourselves against any aggression.

— Javad Zarif (@JZarif) January 8, 2020

State media have reported senior Iranian officials have promised not to launch any more attacks as long as America does not retaliate.

The branch of Iran’s armed forces behind the attacks, which came in two waves, has threatened to target the cities of Dubai, United Arab Emirates, and Haifa in Israel, if bombs are dropped on Iranian soil.

It also warned that if the United States responds with violence in Iran, then “this time we will respond to you in America”.

The second round of attacks started an hour after the first missile launches, Tehran-based Tasnim news agency reported.

The Pentagon confirmed that Iran launched more than a dozen missiles at US military and coalition forces in Iraq.

“It is clear that these missiles were launched from Iran and targeted at least two Iraqi military bases hosting US military and coalition personnel at Al-Assad and Irbil,” Jonathan Hoffman, assistant to the Secretary of Defense for Public Affairs, said in a statement.

Ain Assad air base in Iraq’s western Anbar province was one of the installations targeted.

The base was first used by American forces after the 2003 US-led invasion that toppled dictator Saddam Hussein.

It later saw American troops stationed there amid the fight against the Islamic State group in Iraq and Syria.

Iranian state TV said the operation’s name was “Martyr Soleimani”.

It said the Guard’s aerospace division that controls Iran’s missile program launched the attack. Iran said it would release more information later.

A statement posted on Mashregh, the main Revolutionary Guards news website, confirmed the attacks.

“The time has come to fulfil the promise of the sincere and with the permission of God Almighty this morning in response to the criminal and terrorist operations of the American invaders,” it read.