Iraqi forces backed by helicopter gunships and tanks launched an offensive to retake Tikrit from Sunni Muslim militants who seized the northern city after sweeping south from Mosul.
The troops battling militants from the Islamic State in Iraq and the Levant, also known as Isis, were joined by tribal forces, said former Interior Ministry official Jawad al-Bolani. Tikrit, about 150km north of Baghdad, is the hometown of late president Saddam Hussein.
As many as 7,000 pro-government Sunni fighters and Shiite Muslim volunteers are fighting with the elite forces and other military divisions. They had support from US intelligence to bolster "our security capabilities", said Bolani, who has been assigned to direct and assist the troops.
Meanwhile the Pentagon said armed US drones were now flying over Baghdad to defend American military advisers and diplomats. A senior US official, speaking on condition of anonymity, said "a few" drones were being used to safeguard Americans, but they would not be used for offensive action against the militants.
The Pentagon confirmed some were carrying bombs and missiles.
The US flights come despite the insistence of Prime Minister Nouri al-Maliki that "Baghdad is safe" from militant assault.
Additional reporting by Bloomberg