Three Katyusha rockets landed near Baghdad's airport without causing any damage or injuries, Iraqi army said on Tuesday, in the latest of attacks on military bases.
A rocket launcher was found in a rural area in western Baghdad.
There were no reports of damage or casualties and no immediate claim of responsibility of the attack that took place late on Monday.
A military base near the airport, which is occasionally used by US troops, has come under several attacks this year.
The Iraqi army said that orders had been given to launch an investigation “to reveal these entities that, despite our warnings to them, seek to weaken Iraq.”
Washington accuses Iran-backed militias of carrying out such attacks in the past.
Monday night’s attack is the fourth this month and came just days after Washington and Baghdad launched strategic talks.
The US pledged to reduce the size of its forces in Iraq and confirmed that it does not seek a permanent military presence in the country.
The US-led coalition fighting ISIS has withdrawn from several bases across Iraq in a planned drawdown.
US Assistant Secretary of State David Schenker, in comments to reporters in Washington following the session, said Iraq had committed to “moving ahead and undertaking their obligations,” with regards to militia attacks targeting the American presence.
Iraq, meanwhile, vowed to "protect the military personnel" operating on its territory as part of the US-led coalition fighting remnants of ISIS.
A day before the talks began, a rocket landed a few hundred metres from the US Embassy in Baghdad’s fortified Green Zone.
Tension heightened between the US and Iran after an American drone strike killed Iranian military leader Qassem Suleimani in January near Baghdad International Airport.
It resulted in Iran-backed attacks on American troops stationed in Iraq. The threat of attacks led the US to pull troops out of three Iraqi bases in March.
After the attacks, Iraqi members of Parliament passed a non-binding resolution in January to remove foreign forces from the country.