NORTHERN IRAQ (CNN) -- Kurdish pesh merga fighters, backed by U.S. Special Forces, easily seized the oil-rich northern city of Kirkuk on Thursday, while coalition warplanes pounded deposed President Saddam Hussein's hometown and Iraqi leaders in Mosul offered to surrender.

Thousands of unarmed Iraqi men, partially dressed in civilian clothing, formed a line along the main highway about 100 miles [160 kilometers] northeast of Baghdad, walking barefoot on the hot tarmac toward Kurdish-controlled areas, CNN's Brent Sadler reported Thursday morning. The men identified themselves as soldiers and were described by Sadler as "beaten and defeated."

The men said they had walked for hours or days, and had handed over their weapons to Kurdish forces.

In Baghdad, which U.S. Central Command characterized as "still an ugly place," U.S. troops skirmished with remaining Iraqi forces and were attacked by a suicide bomber.

A battalion from the 173rd Airborne Brigade has reinforced U.S. Special Forces and Kurdish forces in Kirkuk, Maj. Gen. Stanley McChrystal said at Thursday's Pentagon briefing.

"The situation [in Kirkuk] is fluid, and has been all day," McChrystal said.

"Truckload after truckload" of Kurds flooded into the city after the U.S.-backed pesh merga -- ethnic Kurdish guerrilla fighters -- entered the city without a shot being fired by Iraqi defenders, who had apparently headed south toward Tikrit, a Baath Party stronghold and Saddam's birthplace. (Full story)

Kurds dominated the scene in Kirkuk's central square, where they jubilantly followed in the footsteps of Iraqis from the south to Baghdad by toppling a statue of Saddam -- this one in tribal garb -- and dancing on its broken pieces. (On the Scene)

Locals were cheering U.S. troops, who were keeping a "low profile," reported CNN correspondent Jane Arraf.

The pesh merga control nearly 300 villages in northern Iraq.

With the Iraqi forces gone, residents began looting the area -- including a Pepsi soft drink factory said to be owned by Saddam's son, Uday.

CNN correspondent Kevin Sites ran across a large force of Iraqis outside Kirkuk -- apparently soldiers who had shed their uniforms and started off north, away from Tikrit.

Many of those were fleeing the El Haleed military compound, a frequent target of coalition bombers.

Late Thursday, Defense Secretary Donald Rumsfeld said Kurdish troops and U.S. forces from the Army's 173rd Airborne Brigade had entered Mosul, Iraq's third-largest city, and were "being welcomed by the people."

The commander of the Iraqi army's 5th Corps and the governor-general are expected to surrender to U.S. special operations troops in the Mosul area, U.S. military sources told CNN on Thursday. Details were being worked out between the Iraqis and U.S. forces, officers at U.S. Central Command told CNN.

Mosul was one of the coalition's prime targets for the bombing campaign. In the past 24-hours, the coalition flew 1,750 sorties, 550 of them strike sorties, Pentagon officials said. Coalition aircraft launched what officials called their heaviest wave of bombing along the burgeoning northern front early Thursday.

The 5th Corps' combat strength was estimated at 30,000 troops when the U.S.-led invasion of Iraq began March 20, but it is unknown what toll heavy airstrikes and desertions have taken on its three infantry divisions and one mechanized infantry division, U.S. military sources told CNN. Still, the corps' surrender would remove a significant obstacle to coalition control of the city.

In another U.S. troop movement, the first elements of the 4th Infantry Division are expected to begin moving from Kuwait into Iraq within a few days. It is not yet clear if they will move to northern Iraq or help secure Baghdad.