The US Embassy in Iraq has cautioned its citizens against travelling via Baghdad airport through April 8 due to information regarding a "specific threat" to security, ahead of elections later this month.
The statement said embassy personnel were prohibited from using Baghdad International Airport "at this time" and urged American citizens all across Iraq to remain on alert.
No further details were given.
Security officials expect more violence in Iraq in the run-up to elections on April 30 as insurgent groups who have been regaining ground seek to derail or overshadow the voting process.
"US citizens are advised to keep a low profile; vary days, times, and routes of travel; and exercise caution while driving and entering or exiting vehicles," read the statement on the embassy's website.
The United Nations said 592 Iraqis were killed in acts of violence in March.
(Reporting by Isabel Coles; Editing by Sonya Hepinstall)