After months of relative calm in Baghdad, the past week has seen security deteriorate in and around the capital
The US State Department is looking into local media reports that three Americans have been kidnapped by "militias" in Baghdad.
An official said: "We are aware of reports that American citizens are missing in Iraq. We are working with the full cooperation of the Iraqi authorities to locate and recover the individuals."
Scott Bolz, a spokesman for the US Embassy in the Iraqi capital, has confirmed "several" Americans are missing.
Their disappearance was first reported by Al Arabiya, a pan-Arab news channel.
After months of relative calm in Baghdad, the past week has seen security deteriorate in and around the capital - with Islamic State fighters claiming responsibility for a number of attacks in the region which left more than 50 people dead.
One of the deadliest incidents last Monday saw gunmen detonate suicide vests inside one of the city's shopping malls, killing 18 people and injuring 40.