Iraq's third largest city in the north, Mosul, fell to advancing US forces and Kurdish fighters on Friday, apparently without a fight, heralding the total collapse of support for Saddam Hussein in the north.

Within hours, looters descended on public and other buildings in the city, following a pattern of anarchy that has accompanied the fall of the capital Baghdad and other centres across the country.

The US military said the entire Iraqi 5th Corps surrendered in Mosul. "The commander of the Iraqi 5th Corp communicated it to people on the ground," Captain Frank Thorp told reporters at invasion headquarters in Qatar.

Mosul is 390km north of Baghdad. As law and order broke down with schools and other public buildings in Mosul being ransacked, stripped bare or set on fire, there was no sign of US soldiers or of Kurdish peshmerga fighters in the centre of the mainly Arab city.

Elsewhere in the north, US soldiers fanned out across Iraq's largest and oldest oilfield at Kirkuk, the other major northern city, which fell to Kurdish fighters and US special forces without any real fight on Thursday.

Securing the Kirkuk oilfield, capable of pumping 900,000 barrels per day, would leave US-led forces in control of all of Iraq's oil, the world's second largest reserves of crude.

Events in the north left Saddam's native place of Tikrit, which is 175km north of Baghdad on the main road from Mosul, as the one significant target left for the US-led forces.

Both the United States and Iraqi Kurdish leaders, who have run a large slice of the north under the protection of US and British warplanes since, shortly after the 1991 Gulf War, are sensitive to neighbouring Turkey's reaction to the presence of peshmerga fighters in centres outside their zone.

Turkey fears that Kurdish control of Iraq's northern oil fields will fuel separatist aspirations both in northern Iraq and among its own Kurdish minority.

At one stage Ankara threatened to send troops to intervene. Amid reports of the remnants of Saddam's army throwing down their arms and walking away, Kurdish fighters moved into Mosul on Friday, apparently unopposed.

A day earlier they moved unopposed into Kirkuk. Reuters Television producer Soheil Afdjei said the streets of Mosul were initially calm and the mood was one of celebration. "There are a lot people on the streets. There are a lot of Kurdish peshmerga at checkpoints," he added.

US Defense Secretary Donald Rumsfeld had earlier said small numbers of US troops were in the city. But Afdjei said, "I haven't seen any Americans, although the peshmerga say the Americans are in town too."

He watched as jubilant Iraqis, chanting anti-Saddam slogans, entered a branch of the Bank of Iraq and emerged with bundles of Iraqi dinars bearing Saddam's face that some tore to shreds.

Others gathered up the scattered notes and made off with them. "There are no Saddam regime followers left," a Kurdish commander on the city's outskirts said.

A senior Kurdish commander in Kirkuk, 250km north of Baghdad, said his forces were preparing to hand over control of the city to the Americans.

"Yes, we expect to be leaving when the Americans arrive, and that may well be later today," said Mam Rostam, a senior Kurdish commander whose forces had rushed into Kirkuk, apparently without the full agreement of the US.

Five buses were parked outside the main administration building in the centre of the city and fighters there said they had been informed they would probably return on Friday to their positions in their Kurdish-controlled northern enclave.

Kirkuk was quiet early on Friday after a day of jubilation and celebration at the collapse of Iraqi government forces. Dozens of armed peshmerga roamed the streets, but the only US soldiers seen were those from special forces.

Jalal Talabani, leader of the Patriotic Union of Kurdistan, one of the two main Iraqi Kurdish parties, told CNN the Kurdish forces had entered Kirkuk only to secure the oilfields from retreating Iraqi troops and to prevent looting in the city.

"They will go out of Kirkuk immediately when American forces replace them," he said, echoing Rostam's comments. "The city of Kirkuk will be in the hands of American and coalition forces. It will be part of Iraq, the new Iraq, the new democratic, federative Iraq," said Talabani.

Turkish Foreign Minister Abdullah Gul said on Thursday US Secretary of State Colin Powell had told him US troops would remove the peshmerga from Kirkuk.

In Washington, White House spokesman Ari Fleischer said Washington had agreed to Turkey sending a small number of military observers to the area.

(With additional reporting by Mike Collett-White in Kirkuk)