Iraqi troops went on the offensive Saturday, using helicopter gunships, tanks and commandos to weed out Sunni militants who had taken over Tikrit, hometown of former dictator Saddam Hussein.
There were conflicting reports over who had control of the city, part of the large swath of northern and western Iraq seized by extremist militants in recent weeks. Residents said air raids began around the University of Tikrit at dawn.
The offensive in Tikrit, about 95 miles north of Baghdad, came as heavy clashes between Iraqi security forces and insurgents killed at least 21 troops about 30 miles south of Baghdad. Officials says dozens of militants were killed or captured. Separately, Iraq's air force carried out several airstrikes against the city of Mosul, which fell to militants earlier this month.
Shekh Khamis al-Joubouri, a Tikrit tribal leader, told CNN that security forces had retaken Tikrit. But combatants told CNN that fighters from the Islamic State of Iraq and the Levant (ISIL) remained in control.
The pre-dawn raid, backed by helicopter gunships and tanks, includes pro-government Sunni fighters and Shiite militia. The extent of the fighting was unclear and there was no immediate word on casualties. Sabah Numtate-run Iraqiya TV said that Iraqi army forces told the station that 120 militants had been killed and 20 vehicles destroyed.
Tikrit is one of two major cities to fall to ISIL. Muhanad Saif al-Din said the city has emptied out in recent days as locals flee ahead of anticipated clashes.
"Tikrit has become a ghost town because a lot of people left over the past 72 hours, fearing random aerial bombardment and possible clashes as the army advances toward the city," Saif al-Din said. "The few people who remain are afraid of possible revenge acts by Shiite militiamen who are accompanying the army. We are peaceful civilians and we do not want to be victims of this struggle."
The city has been without power or water since Friday night, he said.
The ISIL and its allies have overrun much of Iraq's Sunni heartland, a vast territory stretching west and north from Baghdad to the Jordanian and Syrian borders. After a dramatic initial push, the onslaught appears to have slowed as the militants bump up against predominantly Shiite areas stretching south from Baghdad.
Iraq's U.S.-trained and equipped military melted away in the face of the offensive, sapping morale and public confidence in its ability to stem the militant surge — let alone claw back lost ground. If successful, the Tikrit operation could help restore a degree of faith in the security forces.
It also would provide a boost to embattled Prime Minister Nouri al-Maliki, who is fighting for his job as many former allies drop their support and Iraqis increasingly express doubts about his ability to unify the country.
Al-Maliki, however, has shown little inclination publicly to step aside and instead appears set on a third consecutive term as prime minister after his bloc won the most seats in April elections.
The United States and other world powers have pressed al-Maliki to reach out to the country's Sunni and Kurdish minorities and have called for a more inclusive government that can address longstanding grievances.
Al-Maliki has widely been accused of monopolizing power and alienating Sunnis, who have long complained of being unfairly targeted by security forces.
Iraq is grappling with its worst crisis since the last U.S. troops withdrew in December 2011, raising the specter of the fragmentation of the country along sectarian and ethnic lines.
The United States has watched the turmoil with a wary eye. Already, Washington has already deployed 180 of 300 troops promised by President Obama to assist and advise Iraqi troops.
The United States is flying armed aircraft over Iraq as part of "force protection" measures now that U.S. military advisers have arrived there, the Pentagon confirmed Friday.
The U.S. military said it is flying 30 to 35 missions a day over Iraq, primarily on surveillance missions. "Some of those aircraft are armed," Pentagon press secretary Rear Adm. John Kirby said. The flights included both drones and manned aircraft.
By sundown, Lt. Gen. Ahmed Abu Ragheef, a commander in the Salahuddin Operational Command, said a column of troops had reached the edge of Tikrit, while another had secured an air base that previously served as a U.S. military facility known as Camp Speicher.
The governor of Salahuddin province, Ahmed Abdullah al-Jabouri, told the Associated Press that troops pushed into Tikrit itself, reaching as far the provincial council building.
However, residents reached by telephone Saturday evening said militants were still in control of Tikrit, a predominantly Sunni city of more than 200,000, and patrolling the city's streets.
Contributing: Jim Michaels; Associated Press.