The US embassy in Baghdad has confirmed the kidnapping of several Americans in Baghdad.
Unconfirmed reports from Iraqi security circles also noted that three Americans and an Iraqi translator were seized on the southern side of Baghdad.According to a state department official, they are working together with Iraqi authorities to located the kidnapped Americans.
"We are working with the full co-operation of the Iraqi authorities to locate and recover the individuals," said a state department official.
US officials did not say how many were held or where they were seized.
An official in Baghdad reported to the CNN that three contractors had been missing since Friday.
"A company filed a report on Sunday about three of its staff going missing two days ago. They are American contractors. We are looking into this report," the senior security official said.
"The safety and security of American citizens overseas is our highest priority," said US state department official John Kirby.
If it turns out to be a serious kidnapping, it would be a major blow to hopes for stability and progress in Iraq.
An attack on Baghdad shopping centre, last week claimed by the Islamic State militants, brought to an end a relative lull in violence that had seen no major bloodshed in the city in months.
Before US forces pulled out of Iraq in 2011, a number of Western citizens were kidnapped and killed by radical Shia groups as well as Sunni militants, but none has been abducted since then, our correspondent says.
Last month, a group of Qatari hunters, including members of the ruling family, was kidnapped in the Iraqi desert.