Iran has launched missile attacks on US targets in Iraq in response to the US assassination of Iranian commander Qassem Soleimani last week.
Iranian Foreign Minister Mohammad Javad Zarif said Tehran had taken what it considered to be proportionate measures and did not seek an escalation of war.
In Washington, US President Donald Trump tweeted "all is well!" shortly after the missile attacks in the early hours of Wednesday, adding that an assessment of casualties and damage from the strikes was under way.
Here is what we know so far:
At about 01:30, Iran fired more than a dozen ballistic missiles from its territory against at least two Iraqi facilities hosting US-led coalition personnel, the US military said.
The missiles hit two bases: Ain al-Asad in Anbar province and a facility in Erbil, the capital of Iraq's semi-autonomous Kurdish region.
The Iraqi military said two of the 17 missiles targeting Ain al-Asad base did not go off. The five on Erbil all targeted coalition headquarters.
No casualties have been officially confirmed so far.
The Iraqi military said there were no casualties among its forces.
Germany, Poland, Norway and Denmark also said that none of its soldiers stationed in Iraq were wounded or killed, according to reports.
Iranian state television claimed that at least 80 "American terrorists" were killed in attacks involving 15 missiles, adding that none of the missiles were intercepted.
The claim could not be independently verified and the state television did not provide evidence of how it obtained that information.
How did we get here?
Iran's Islamic Revolutionary Guards Corps confirmed they fired the missiles in retaliation for last week's killing of Soleimani, according to a statement on state media.
US officials have said Soleimani was killed because of intelligence indicating forces under his command planned attacks on US targets in the region. But they have not provided evidence.
A war of words between US and Iran had been waging since Soleimani's assassination, and Tehran had pledged a "harsh response" to avenge his death. US President Donald Trump threatened to hit 52 Iranian sites "very hard" if Iran attacked US citizens or assets.
War of words ... for now?
In a speech in Tehran after the attack, Iran's Supreme Leader Ayatollah Ali Khamenei said: "The corrupt presence of the US in the region should come to an end", calling the missile strike a "slap in the face" of the US.
Trump said in his tweet that he will make a statement on Wednesday morning. Amid the rising tension, governments around the world have called for a return to diplomacy.