Around half a million people have been forced to flee Mosul, Iraq's second city after a takeover by the armed group Islaming State of Iraq and Levant (ISIS).
Iraqi soldiers were among those fleeing, mainly to Kurdistan.
Residents of Mosul said that militants from the group, also known as ISIL, an offshoot of Al-Qaeda, announced over loudspeakers that they had "come to liberate" the city.
A spokesperson for the US State Department said on Tuesday that the "US is deeply concerned" about the recent events and also pledged to provide "all appropriate assistance to the Government of Iraq."
See more on the BBC.