Four rockets exploded inside Baghdad's fortified Green Zone near the US embassy, Iraq's military said on Thursday.
It is the third such attack since the US embarked on strategic talks with Iraq's new government.
It was not immediately clear who was responsible for the attack, which caused no casualties or damage, but the US has blamed Iran-backed militia groups for a recent quick succession of rocket attacks targeting the American presence in Iraq.
The attacks are proving to be a key challenge for the administration of prime minister Mustafa al-Kadhimi, whose government has promised to take action against militias who attack the US.
Thursday's attack was the third since strategic talks were launched last week.
In a tweet following the attack, Mr al-Kadhimi said it aimed to "undermine our stability and future" and was "unacceptable".
"I will not tolerate rogue groups hijacking our homeland to create chaos and find excuses to maintain their narrow interests," he said.
The first session of the much-anticipated talks between the US and Iraq began last week and laid the agenda for the months ahead, including the issues of the presence of US troops in the country, militia groups acting outside of state authority and Iraq's dire economic crisis.
During the talks, Iraq committed to "moving ahead and undertaking their obligations" to protect the US presence against militia attacks, said US assistant secretary of State David Schenker.
But attacks have continued in an apparent defiance of that promise.
A military statement said four rockets struck the Green Zone, which houses government buildings and foreign embassies including the US, just after midnight on Thursday.
The statement said there were no casualties or material damage.
Security forces later found a Katyusha rocket launching platform near Al-Rashid camp south of the capital.
On Monday, three rockets landed after midnight in the vicinity of Baghdad airport, a military statement said.
The launch was from the al-Makaseb neighbourhood, a police investigation later found.
On Saturday, two rockets hit Camp Taji base, north of Baghdad, without causing casualties.
The base is frequented by US troops.