The U.S. embassy in Baghdad urged American citizens to leave Iraq immediately on Thursday.
The embassy warned that Iran-aligned militias may be planning attacks in central Baghdad within the next 24 to 48 hours targeting Americans, businesses, diplomatic facilities, hotels and airports.
The warning comes two days after American journalist Shelly Kittleson was kidnapped in Baghdad by suspected Kataib Hezbollah operatives.
"Do not travel to Iraq for any reason. Leave immediately if you are there," the embassy said in a security alert posted on X.
The embassy said potential targets could include "US citizens, businesses, universities, diplomatic facilities, energy infrastructure, hotels, airports, and other locations perceived to be associated with the United States, as well as Iraqi institutions and civilian targets."
It noted that militias have previously targeted Americans for kidnapping, a reference that follows the abduction of Kittleson on Tuesday.
The U.S. government is currently working to secure her release.
The embassy also said routine consular services had been suspended and urged all U.S. citizens to depart without delay.
In one of its most pointed assessments, the embassy said the Iraqi government "has been unable to prevent terrorist attacks originating from or within Iraqi territory."
It added that "some terrorist militia groups may be linked to the Iraqi government, and some terrorists may even carry identification documents indicating they are Iraqi government employees."
The warning reflects longstanding U.S. accusations that some Iraqi militant groups maintain ties to Iran and have carried out attacks on American bases in the region since the conflict began.
Iran-backed militias in Iraq have launched regular attacks on U.S. facilities since the U.S. and Israel began their air offensive on Iran on Feb. 28, killing more than 1,340 people, including then-Supreme Leader Ali Khamenei.
Iran has retaliated with drone and missile strikes targeting Israel, Jordan, Iraq and Gulf countries hosting U.S. military assets, causing casualties and infrastructure damage while disrupting global markets and aviation.
The U.S. embassy in Iraq has repeatedly warned citizens to leave the country since the conflict began in late February.
Iraq remains at a Level 4 travel advisory, the State Department's highest warning level.