Following four days of sporadic firefights and bombing, about 140 U.S. troops today made their deepest incursion to date into this riverside city to seize a water treatment plant suspected to be an observation post for Iraqi forces.

Only some brief mistargeted shooting came toward the plant as Americans from the 82nd Airborne Division took it over. Several Iraqi men were spotted -- and one killed -- trying to set up a mortar to target the seized facility.

U.S. officers viewed the scant resistance as something of a turning point for control of the city, located on the supply lines of U.S. Army and Marine forces moving on Baghdad.

U.S. snipers took up position on the plant's roof for a clear view of the city's core, and loudspeakers hauled to the site blared messages toward a dense residential sector. "You are surrounded by elite U.S. forces," a taped voice announced in Arabic. "Cease resistance now so that you may live."

In the afternoon, eight people wandered forward to surrender. A group of several hundred more appeared to be considering the offer as more shelling rocked parts of the city.

"They're just standing on the edge of town, like they're trying to figure out what they should do," said Capt. Patrick Willis, a spokesman for the division's 2nd Brigade. "They've been there all day."

Three battalions from the division began surrounding Samawah, a city of about 140,000 people, last weekend, trying to prevent Iraqi soldiers and paramilitary fighters loyal to President Saddam Hussein's Baath Party from staging ambushes on nearby U.S. supply lines.

The division has tried to turn the tables by choking off supplies to the Iraqi fighters. The Americans now control key roads and bridges to prevent reinforcements of ammunition and fighters from reaching the city.

On Tuesday, other U.S. battalions pushed into the east side of the city to take control of a bridge spanning the Euphrates River near the city center. Numerous bombings have targeted suspected paramilitary hideouts, weapons caches and local Baath Party headquarters. One U.S. soldier has died in the fighting, and 11 others have been wounded.

Fierce firefights near a bridge over the Euphrates ran for nearly four hours, killing one U.S. soldier and wounding seven.

Today the division fired artillery and cluster bombs at a soccer stadium where leaders of the city's paramilitary forces were believed to be gathering with many of their vehicles. Those attacks killed six and wounded 20, according to Willis.

Officers in the 325th Infantry Regiment said ambushes on supply lines have stopped since the U.S. attacks.

When they seized the treatment plant today, the soldiers found a guard post stained with pools ofblood from fighting the day before.

Searching several houses adjacent to the entrance, they found a family of 12 in one of the houses, including an employee of the plant. He led officers to several weapons that were being stored in the plant, including rocket-propelled grenades and machine guns. The man also told commanders that the city's newly appointed Baath Party governor had fled the city.

"They're just trying to back down and stay alive right now," Willis said.