Iraq: Kerry pledges US help over al-Qaeda militants
5 January 2014 Last updated at 20:09 GMT
Iraqi residents inside the city of Fallujah in the western Al-Anbar province have told the BBC that there is an exodus of families to nearby villages and cities to flee heavy artillery bombardment and air strikes by the army.
The assault comes after tribal fighters and al-Qaeda militants asserted full control of the city.
The US Secretary of State, John Kerry, said Washington would provide assistance to Iraqi forces in their battle but would not send in American troops.