At least one Katyusha rocket was fired into Baghdad's Green Zone diplomatic quarter close to the US embassy on Sunday night.
The attack in the Iraqi capital comes just days after the US embassy said that the State Department had instructed all non-emergency US government employees to leave Iraq amid a heightened security threat from Iran and its proxies.
It called on US personnel to leave Iraq by commercial transport as soon as possible and to avoid US buildings in Iraq.
Witnesses to the attack reported hearing a rocket overhead, with claims it had been fired from a bridge.
The rocket caused no casualties, Iraqi officials said.
Police were searching for suspects in the area and said the US embassy was not hit.
The attack was not an escalation in regional conflict, the Iraqi Oil Minister said.
“It’s not the first time it’s been shelled,” Thamir Ghadhban said in Jeddah. "I don’t take it seriously at all. This is an isolated incident. It can be handled."
The Katyusha rocket launcher is an inexpensive type of rocket artillery that can deliver explosives to a target quicker than conventional artillery, but is less accurate.
“We are aware of an explosion in the green zone outside of the US embassy Compound in Baghdad on May 19," US Central Command told CNN.
"No US casualties have been reported at this time, and Iraqi Security Forces are investigating the incident."
US Secretary of State Mike Pompeo made an unexpected trip to Baghdad this month to ensure the country could adequately protect Americans amid an increased threat from Iran.
The Trump administration has sent more troops to the region to counter what it called credible threats from Iran against US interests, including from militias it supports in Iraq.
Tension between the two countries has been escalating, despite both of them previously saying they did not want a war.
But on Sunday, US President Donald Trump appeared to change tack, tweeting: "If Iran wants to fight, that will the official end of Iran. Never threaten the United States again."