The attack came hours ahead of an extraordinary parliament session that will vote on the proposed government of the latest prime minister-designate, Mustafa al-Kadhimi.
After weeks of negotiations and changes to his ministerial lineup in an effort to appease political blocs, al-Kadhimi's Cabinet is believed to have a chance at passing. He is the third premier candidate to be chosen since Prime Minister Adel Abdul-Mahdi resigned in December.
Shortly after the Katyusha attack, Iraqi security forces later discovered the launching pad for the rockets in the al-Barkiya area, west of Baghdad. No group immediately claimed responsibility.
An Iraqi security official, speaking on condition of anonymity in line with regulations, said one of the rockets struck close to Iraqi forces at the military airport, another near Camp Cropper, once a U.S. detention facility, and the last near to where U.S. forces are stationed at the base. Sadaam Hussein was held in Camp Cropper prison prior to his execution.
The U.S. has accused Iran-backed militias of carrying out such attacks in the past. Several attacks targeted U.S. interests early in March, including three military bases known to house U.S. troops. The U.S.-led coalition has withdrawn from several bases across Iraq in a planned drawdown.
The attack is the first following a brief lull since March 26, when rockets struck near to the Baghdad Operations Command, a center that coordinates Iraq's police and military forces. The command is a few hundred meters (yards) from the U.S. Embassy, which has also been a frequent target of rocket attacks.