U.S. and Iraqi authorities are searching for three American contractors reported missing on Sunday from a neighborhood in Baghdad, with unconfirmed reports claiming they were kidnapped by gunmen, according to The Washington Post. 

"We are aware of reports that American citizens are missing in Iraq," said John Kirby, a State Department spokesman. "The safety and security of American citizens overseas is our highest priority."

A senior security official in Baghdad told CNN that the contractors went missing in Iraq two days ago. "A company filed a report Sunday about three of its staff going missing two days ago. They are American contractors. We are looking into this report," said the official,  according to CNN.

After months of relative calm, tensions have escalated in and around the Iraqi capital this week with security said to be deteriorating. Last week, more than 50 people were killed in attacks linked to the Islamic State group in Baghdad and Diyala, including an attack on a popular mall, according to Fox News.

"We are working in full cooperation with Iraqi authorities to locate the missing Americans," said U.S. Embassy spokesman Scott Bolz. 

A report from the satellite channel al-Arabuya said the Americans were abducted by "militias" in the area of Dora in the city's south, according to The Washington Post. 

Both Sunni and Shiite militants are present in Baghdad, with many of the Iran-backed Shiite militias known to operate as powerful forces in Iraq. It's undetermined if this incident with the missing Americans has anything to do with the recent release of four Iranian-American prisoners in Iran, as reported by HNGN.