Updated

The U.S. Army occupied Mosul from the air and on the ground Tuesday with little resistance except scattered small-arms fire, taking custody of a northern city they said was in good shape for quick rehabilitation once the security situation improves.

Troops occupied key government buildings, medical clinics, a television station and power plants as they moved in.

Mosul, Iraq's third-largest city, is home to several ethnic groups, including Arabs and ethnic Kurds, who share it uneasily. Marines had been holding parts of Mosul, including the airfield, awaiting the Army's arrival. Last week, 17 Iraqis were killed in confrontations with American forces in Mosul, local hospital officials said.

"If people would stop shooting at each other, then the place would be all right," said Maj. Gen. David Petraeus, commander of the 101st Airborne Division. "The bottom line is, if we provide security in Mosul, it will blossom on its own."

Over eight hours Tuesday, the 101st's 2nd Brigade flew in 1,500 soldiers and sent in 1,000 more overland, bringing to at least 3,500 its complement there, according to Col. Joseph Anderson.

Iraqis waved at U.S. troops arriving on Mosul's roads, then went about their business as American forces spread out around the city. On Thursday, they plan to open an information area in the center of the city to begin humanitarian assistance and to start restoring services.

American forces came under some small-arms fire at the airfield, but said they suffered no injuries. They sent out assault helicopters to chase the assailants; it was unclear if they caught the gunmen.

"We've got to deal with the remaining military and paramilitary in the city, who continue to snipe at our soldiers," Petraeus said.

Anderson agreed, but said the larger resistance expected didn't surface.

"The report we got was we'd have to fight our way in. It's gone from one extreme to the other," he said. "We're all over it. We have occupied it."

A view from the air bore that out. Military vehicles lined the streets of town, clustered near a former government building next to a vacated jail that Army forces commandeered as their headquarters. People hung laundry on rooftops and tended farm animals.

There was little visible damage from U.S. bombardment except for one military compound used by Saddam Hussein's army.

On the grounds of Saddam's palace in Mosul, the curious had flooded the place -- not to loot, U.S. forces said, because everything was already pillaged. They just wanted to see the palace.

An Army 4th Infantry Division tank battalion attached to the 101st also rumbled in Monday. Parts of the 101st remain in southern Baghdad, and other parts of it are in the southern city of Karbala.