The apparent departure by militants suggests there will be no need for major battles to reclaim two Iraqi cities in the western Anbar Province invaded last week by the Al-Qaeda-linked fighters.
Correspondents from RFE/RL's Radio Free Iraq reported that gunmen from the Islamic State in Iraq and the Levant (ISIL) were leaving the city of Fallujah and were headed in the direction of the desert.
The militants' withdrawal comes after Iraqi government forces moved into positions around Fallujah preparing for a major assault on the city.
Tens of thousands of civilians have been fleeing Fallujah in recent days.
Prime Minister Nuri al-Maliki has been urging Sunni tribes to take action on their own to oust the ISIL militants.
In Ramadi, the capital of Anbar Province, security forces were reportedly fully in control of the city as of January 8 after ISIL militants left that city.
Some businesses, including banks, shops and bazaars opened again the same day.