A Katyusha rocket landed in Baghdad's heavily fortified Green Zone, causing damage to an empty building and no casualties, Iraqi police sources said on Saturday, Reuters reports.
Sirens blasted from the U.S. embassy inside the zone, which houses government buildings and foreign missions, and helicopters were hovering above, the sources said.
It was the second such attack this week after three rockets landed in the Green Zone on Thursday, also causing no casualties.
Washington blames such attacks on Iranian-backed militia groups. Iran has not directly commented on the incidents but little-known groups believed to be connected to Iran-aligned militias have claimed some attacks.
Iraq, often the scene of spillover violence from U.S.-Iran tensions, seeks to avoid being drawn into any regional conflagration.
The Middle East came close to a full conflict in January after a U.S. drone strike killed Iranian General Qassem Soleimani and Iraqi paramilitary chief Abu Mahdi al-Muhandis at Baghdad airport.
Iran-aligned militias have sworn to avenge their deaths.