U.S. officials expressed outrage Monday after a trio of rockets slammed into Baghdad, two of them landing in the city's fortified Green Zone.
Iraqi officials said the Katyusha rockets appeared to have been launched from a nearby neighborhood but that no one was injured.
Iraq's military said four vehicles were damaged, along with some property.
Initial reports indicated the rockets that hit inside the Green Zone landed close to the U.S. Embassy and also close to Joint Operations Command, where U.S. military personnel coordinate with the Iraqi military in the fight against the Islamic State terror group.
No one claimed immediate responsibility for the attack, which comes just a week after a rocket attack outside Irbil International Airport, in northern Iraq, killed a contractor for the U.S.-led coalition and injured nine others, including a U.S. military member.
"We are outraged by the recent attacks," State Department spokesman Ned Price told reporters Monday. "The Iraqi people have suffered for far too long from this kind of violence, and this violation of their sovereignty."
So far, U.S. officials have refused to assign blame for the attacks, though Saraya Awliya al-Dam, a Shia militia, has claimed responsibility for the deadly attack in Irbil.
Pentagon press secretary John Kirby said Monday that military officials are taking the attacks "very seriously."
"It's difficult to say with certainty ... whether there's a strategic calculation driving this recent uptick in attacks or whether this is just a continuation of the sorts of attacks we've seen in the past," he said.
And while the investigation into the attacks is ongoing, Kirby said, "If and when it's appropriate to respond, we'll do so at a time and a place and a manner of our choosing."
A number of U.S. lawmakers have raised concerns that the recent string of rocket attacks, like previous ones, likely was orchestrated by Iran.
U.S. defense officials have consistently blamed Iran for being the main driver of instability across the Middle East, but add they are comfortable the number of U.S. troops in the region are sufficient to deal with the threat.
"Broadly, what we have said is that we will hold Iran responsible by the attacks, by the provocations of its proxies," the State Department's Price told reporters. "What we will not do is lash out and risk escalation that plays into the hands of Iran and contributes to their attempts to further destabilize Iraq."
VOA's Nike Ching, State Department correspondent, contributed to this report.