Two rockets have been fired at the US embassy in Baghdad, according to security sources.
Alarms have reportedly been going off after the missile struck the Green Zone around the Iraqi capital at around 9.30pm local time.
People in the vicinity have been urged to take shelter immediately.
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There are no reports of immediate casualties.
The US has blamed Iran-backed paramilitary groups for a spate of similar attacks in recent months on the Green Zone, but there has never been a claim of responsibility.
Earlier this month, two military bases housing US troops in Iraq came under fire from at least a dozen ballistic missiles, triggering a heightening of tensions between the US and Iran.
Iranian state TV said Tehran had launched "tens" of surface-to-surface missiles at the Al Asad airbase in response to America's killing of Qasem Soleimani, a top Iranian general.
On Monday this week, newly appointed commander of Iran's elite Quds Force, Esmail Qaani, remarked that Iran would "hit its enemy in a manly fashion" in retaliation.
"(The US) hit (Soleimani) in a cowardly way, but with God's grace and through endeavours of freedom-seekers around the world who want vengeance over his blood, we will hit his enemy in a manly fashion," he said yesterday.
Iran's Supreme Leader Ali Hosseini Khamenei has called for the expulsion of all American troops from the Middle East.