Reports Saturday say the Iraqi government has lost control of Fallujah to al-Qaida militants after days of fighting.
A senior security official told the French news agency that Fallujah is under the control of ISIS - a reference to the al-Qaida-linked group, the Islamic State of Iraq and Syria.
Witnesses says there are no signs of government forces inside the Anbar province city, which is only 60 kilometers west of Baghdad.
On Friday, al-Qaida militants raised their flag over government buildings in Fallujah and declared an independent Islamic state.
Witnesses said the militants cut power lines in the city late Friday and ordered residents not to use backup generators.
A local journalist who asked for anonymity out of fear of retribution told The Washington Post that police and other government-aligned forces had abandoned the city and that al-Qaida had burned all Iraqi national flags.
Fighting across the vast open spaces of western Iraq has become a severe test of Prime Minister Nouri al-Maliki's ability to hold the country together and prevent full-scale civil war.
Meanwhile, in the Anbar provincial capital, Ramadi, a tribal leader who fought alongside U.S. troops in 2007 told The Washington Post his fighters had joined police in ejecting al-Qaida loyalists. He said the regional ISIS leader, Abdul Rahman al-Baghdadi, was among those killed in the fighting.
The explosion of violence in western Iraq is pitting al-Qaida-linked Sunni extremists, who now control large swaths of the region west of Baghdad, against forces of the Shi'ite-dominated central government. Government forces in the west are backed by local tribesmen who have chosen to align themselves with Baghdad rather than with ISIS fighters.
Anbar province was the center of the Sunni insurgency during the eight-year presence of U.S. military forces, which withdrew from the country in December 2011. More than 1,300 U.S. military personnel were killed in the region.