This city was swept by determined, almost methodical looting by Kurds for a second day before U.S. forces, cloistered on the outskirts, began to move in to stem the anarchy that has ruled Kirkuk since it was abandoned by Iraqi authorities.

Kurdish officials, whose forces did nothing until this evening to discourage looting, earlier in the day criticized the U.S. military for not filling the authority vacuum in Kirkuk after pushing out the Baath Party rulers a day earlier.

"America does everything but doesn't think about the next day," said Faraidoon Abdul Qadir, interior minister for the Patriotic Union of Kurdistan (PUK), one of the two groups whose militia entered the city Thursday. "They don't coordinate with us."

U.S. commanders had initially decided against launching patrols, focusing instead on holding strategic sites in the city, including oil facilities and airfields. But late in the day they sent two convoys of a half-dozen vehicles on a six-hour patrol through the city. The second patrol encountered several near-riots and a firefight between Turkmen residents and Kurdish looters.

"We've got to get out on the streets and let them know the U.S. is in control," Brig. Gen. James Parker, commander of U.S. forces in northern Iraq, told brigade officers this afternoon.

As dusk gathered over a city without a sanctioned authority or electricity, Kurdish militiamen in black berets began an abrupt crackdown on looting at a downtown intersection. The militiamen cocked their assault rifles and slapped the windshields of any vehicles loaded with cargo, allowing angry men to clamor aboard and spill the booty onto the street.

"Why? Why are you stealing our things?" screamed a man tipping cardboard boxes off a stopped truck. A gathering crowd made a snowstorm out of the medical cotton they found inside, then scrambled for cover as the militiamen ripped several volleys into the air.

Moments later, utility vehicles roared into the intersection and disgorged young men armed with Kalashnikov rifles. The new arrivals stood guns-up and watchful. In the gathering darkness, it was hard to tell who was who.

Earlier in the day, small teams of U.S. Special Forces moved between appointments in convoys of white Land Rover Defenders, but joined in nothing that resembled patrols.

Most of the reported 2,000 troops of the 173rd Airborne Brigade, which arrived overnight, remained largely out of sight in a pair of airports at the edge of the city. U.S. and Kurdish officials spoke of plans for the American troops to replace Kurdish pesh merga on the streets, but no timetable was given.

At midafternoon, U.S. officers met with officials from the four ethnic groups that make up Kirkuk's population of 1 million. Parties representing Turkmen, Kurds, Arabs and Assyrians gathered in a building formerly occupied by the Baathist governor with the goal of forming a coalition to temporarily govern the city.

No formal arrangement was reached, but the effort was intended to show Turkey that the Kurds would not rule Kirkuk alone. Turkey's government, which is wary of any move toward an independent Kurdish state, opposes Kurdish control of Kirkuk or its nearby oil fields. "The key is the operative word -- coalition," said Barham Salih, prime minister of the PUK.

Calling for an "orderly transition to democracy," Salih called the looting "very unfortunate. We're disappointed."

He added, however, that "compared to other towns, Kirkuk is more orderly."

That appeared to be the case for much of the day. Families strolled down streets that a day earlier had been crowded with celebrating Kurdish militiamen. Saddam Hussein's government had forced 120,000 Kurds out of the area, most of whom found refuge in the autonomous Kurdish region just to the north, which has been protected by U.S. warplanes.

A few fires smoldered in government buildings set alight the day before. Smoke from a handful of fresh blazes smudged the blue sky. A burning ammo dump at one of the city's numerous military bases crackled like firewood.

Human rights monitors said that, with no immediate reports of revenge killings, the situation appeared better than they expected. "You need a few days for things to percolate," said Eric Stover, a researcher for Human Rights Watch, the advocacy group based in New York.

Residents, long accustomed to sharing the city with members of other ethnic groups, professed no worries about the future.

"We are just ordinary people," said Atella Faisal, a Turkman barber. "We seek only peace and freedom. We don't care who rules the city."

Murad Ali, a Turkmen teacher, opposed Turkey's threat of sending troops in the name of protecting Kirkuk's Turkish-speaking citizens. "I don't want them here," Ali said. "We just want peace."

But the Iraqi Turkmen Front, an exile group closely associated with Turkey, called for Ankara to intervene. "There are many people who come here to us saying they want weapons to defend ourselves," said Ali Mahdi Sadek, who just arrived from Germany.

"We have to have weapons."

Ali, the Turkmen teacher, called the looting a reaction to Baghdad's campaign to "Arabize" Kirkuk by denying property rights to Kurds while paying Arabs to move to the city, in some cases taking over the homes of Kurds.

"At that time, we got 6,000 dinars and an apartment in one of these buildings," said Sabiha Atya, 40, gesturing toward a block of decrepit walk-ups ringed by wet rubbish.

Atya arrived in Kirkuk with her husband 12 years ago. "So many people came. We were vulnerable, living in poverty. That's why we were obliged to come."

The mother of five then excused herself, explaining she was joining her husband and son in scouring a former Baath security building for anything that might be of value.

Even at the airfield, where every building and vehicle had already been ransacked by pesh merga militiamen Thursday, people wandered around, looking for more items to grab. Parker, the U.S. commander, directed that they be allowed to leave with what they could carry, but that no more looters be allowed on the airfield.

The patrols will make their presence known around hospitals and important infrastructure in the city, U.S. officers said.

To heighten its presence, the brigade occupied a second airfield today closer to the city center and moved its base of operations there. .

"We have to do things that assure people that this will not get out of hand," said Col. William Mayville, commander of the brigade.

The U.S. force also expanded its hold on key oil facilities around the city today. The 2nd Battalion, 503rd Infantry, which occupied an oil stabilization facility Thursday evening, sent troops to two other key facilities. U.S. Special Forces are watching over four gas-oil separation facilities, officers said.

"When you want to send the message, 'Hey, don't screw with the oil,' coming here was important," Mayville said during a tour of one of the facilities.

But it will be impossible to completely protect Kirkuk's expansive oil fields and numerous oil facilities, he said. "What do you secure here?" he said, pointing to pipelines. "Look how vast it is."

The brigade faces other challenges as well. The force might have to process Iraqi prisoners of war, including a group of 1,100 Iraqi soldiers who commanders were told are in hiding in Kirkuk, waiting to surrender.

A Kurdish militia member confronts a looter in Kirkuk. Looting overtook the northern city as U.S. forces remained mainly on the sidelines for much of the day.Soldiers from the 173rd Airborne Brigade are cheered in the streets of Kirkuk, where they are soon to begin patrols.