KIRKUK, Iraq - Hammered by U.S. air strikes and facing thousands of advancing Kurdish rebels, Iraqi forces yesterday cast aside their weapons and fled Kirkuk, relinquishing intact one of the Middle East's richest oil fields.

The city sits atop 10 billion barrels of proven reserves. Only one oil well was set on fire before the abrupt departure of Iraqi forces, Baath Party militia and paramilitaries loyal to Saddam Hussein.

The fall of the northern cities of Kirkuk and Mosul without a strong fight left a handful of key towns and cities outside the control of U.S.-led troops after 22 days of fighting.

Iraqi army troopers, Baath Party officials and paramilitary members fled Mosul yesterday afternoon. U.S. special forces teams moved in late in the night as residents began looting shops and celebrating by firing their Kalashnikovs in the air in the mostly Arab city, Iraq's third largest.

About 2,000 Kurdish guerrilla fighters moved into Mosul's suburbs in pickup trucks, tractors, taxis and buses and prepared for a full-scale advance early this morning, awaiting orders from special forces.

The mostly Kurdish city of Kirkuk, meanwhile, exploded in riotous celebrations of its new-found freedom and outpourings of pent-up hatred for Hussein. Crowds took to the streets in cars, trucks and on foot, dancing, cheering, singing, waving U.S. flags and portraits of Kurdish leaders, kissing U.S. special forces, and letting loose bursts of automatic-weapons fire well into the evening.

"I have been waiting for this day from my birth," exclaimed Nawzad Noori as he drove his wife and two daughters past what was the headquarters of Hussein's Baath Party.

At least two people were killed, and more than 14 were wounded by bullets fired into the air.

The fall of the city of 600,000 came unexpectedly a day after U.S. forces took control of central Baghdad.

At 5 a.m. yesterday, thousands of peshmerga (Kurdish rebel fighters) and small units of U.S. special forces began advancing into Kirkuk from several directions. About 11 a.m., after intense gunfire and mortar exchanges, a B-52 bomber blasted Iraqi positions with nine to 12 bombs. An additional four were dropped a short time later.

Kirkuk residents and several Iraqi army soldiers who stayed behind said that under pressure from the approaching peshmerga and the air strikes, officers and Baath Party members shed their arms and uniforms, put on civilian clothes, and fled.

"They just wanted to keep their lives," said Riaz Jihad Zahir, an Iraqi army conscript from Nasiriyah, as he and several colleagues strolled back into the city from their frontline positions. "We did not fight. We just retreated."

Hundreds of troops were seen on a highway east of Kirkuk, apparently making their way home. Others were believed to be headed southeast toward Hussein's hometown of Tikrit.

Once they realized that they no longer faced Iraqi opposition, peshmerga from the Kurdistan Democratic Party and Patriotic Union of Kurdistan, the two main U.S.-backed Kurdish rebel groups, streamed into the city to ecstatic greetings.

Meanwhile, a company from the 173d Airborne Brigade took up positions around the field and established a headquarters in a building at an abandoned airfield. The brigade's first task will be to secure oil fields and airfields but not go into the central city, officers said.

Kurdish officials said thousands of Kurdish fighters who flooded the city would withdraw as U.S. troops enter. It was not immediately known when the handover would take place.

"There is confusion within the city, and people are doing deeds that are not good. Now American forces are here, and we are trying to put the city under their control."

The planned takeover of security by U.S. troops appeared to eliminate the possibility of military intervention by Turkey, which threatened to invade northern Iraq to prevent Kurdish control of Kirkuk.

Ankara fears that the Iraqi Kurds could harness the city's oil resources to fund an independence drive that would reinvigorate a secessionist movement among Turkey's large, poorly treated Kurdish minority.

Secretary of State Colin L. Powell spoke to Turkish Foreign Minister Abdullah Gul yesterday, pledging that the United States would not permit Kurdish forces to control Kirkuk, U.S. officials said.

Powell confirmed that Turkey would station military liaison officers with U.S. military forces in the Kirkuk area, State Department spokesman Richard Boucher said.

U.S. officials hope the move will assuage Turkey's concerns and prevent it from trying to send thousands of troops into northern Iraq.