U.S. troops stormed into the heart of Baghdad on Monday, seizing Saddam Hussein's New Presidential Palace on the Tigris River in a brazen daylight raid to show that Americans could enter the capital any time, anywhere.

U.S. tanks also briefly surrounded the Information Ministry and Al-Rashid Hotel.

More than 70 tanks and 60 Bradley fighting vehicles took part in the raid under cover of tank-killing A10 Warthog planes and pilotless drones.

Four or five Marines were killed when their armored troop carrier took a direct hit from artillery shell at a bridge over a canal on the outskirts of Baghdad, according to Lt. Col. B.P. McCoy of the 3rd Battalion, 4th Marines. About a half hour later, Marines swarmed into the capital on foot, crossing a bridge spanning a canal at the south edge of the city, meeting little resistance.

There was no estimate of Iraqi casualties from the raids, but 10 miles outside the capital, about 100 Iraqis in military uniform were killed in fighting at Baghdad International Airport in a seven-hour battle that ended at 1 a.m. Monday.

Capt. Frank Thorp, a Central Command spokesman, characterized the movement as another raid through the city and not a seizure of any territory or targets.

When asked if U.S. troops would remain inside Baghdad, Thorp said he would not discuss future plans.

"What you're seeing here is similar to what we saw on Saturday, with an armored raid through the city," he said.

Tanks of the 2nd Brigade of the 3rd Infantry Division barreled into the capital on the western side of the Tigris at 6 a.m. As they approached Baghdad along Highway 8, they met moderate resistance -- mostly assault fire and rocket-propelled grenades from infantry.

"I do believe this city is freakin' ours," boasted Capt. Chris Carter of Watkinsville Ga.

However, Iraq's information minister declared, "I reassure you Baghdad is safe."

"They are beginning to commit suicide at the walls of Baghdad," Information Minister Mohammed Saeed al-Sahhaf told reporters in a hastily called news conference outside the Palestine Hotel. "There is no presence of the American columns in the city of Baghdad, none at all."

The U.S. Army columns moved northeast to the newest and main presidential palace on the river, which divides the capital. The palace, which is near Saddam's Baath Party headquarters, apparently was mainly residential rather than used for administrative purposes. The party headquarters have been destroyed, although it wasn't clear when the damage was done.

Iraqis -- some nearly naked -- fled along its banks. Some jumped into the water. An ammunition depot across the river was on fire.

Before the Americans seized the complex, Iraqis shot small arms fire at them from a clock tower overlooking the compound. Tanks quickly destroyed it.

Attack Company, 3rd Battalion, 7th Infantry entered the palace compound. Inside the bombed-out palace, troops rifled through documents and inventoried the building. Some rooms had spectacular river views. A thick layer of dust covered gilded, imitation French baroque furniture.

The main palace building -- sand-colored brick ornamented with blue tile -- was flooded in the basement and first floor. The rest of the building appeared to be destroyed, hit by cruise missiles or laser-guided bombs.

Palace curtains were strewn over the ground, blown from their windows by the explosions. Most of the compound was severely damaged from prior U.S. raids.

Col. David Perkins told his troops before the operation that the mission was intended to be a demonstration of force to prove that U.S. forces could move about the city at will.

He said another palace on the eastern side of the Tigris was being attacked. "I hope this makes it clear to the Iraqi people that this (the regime) is over and that they can now enjoy their new freedom," Perkins said.

Perkins said the resistance coming into the city was heavier than expected: He had thought most Iraqi defenses were wiped out Saturday, but Iraqi troops laid new minefields and set up many new firing positions.

On entering the city, the Bradleys and tanks took up fighting positions around the presidential palace.

U.S. troops had to pass through a 400-yard-long minefield to approach the area. About 200 anti-tank mines that had been scattered on the road were pushed aside by U.S. armor fitted with devices to move them without detonating them.

"I think it's a good testament to the American soldier," Perkins said. "In the last 17 days -- over 500 miles and heavy, heavy fighting on many days -- to finally be here is a great accomplishment."

U.S. forces also briefly surrounded the Information Ministry and Al-Rashid Hotel, which was used by foreign reporters as a base during the 1991 Gulf War. At the time, the U.S. government alleged that the building housed a military communications center.

After the Americans moved on Monday, armed Iraqi militiamen were at the gate of the ministry and Iraqi army troops were at one corner of the building. Militiamen behind sandbags cheered at passing media buses. A lone woman in black walked in the middle of street.

As U.S. troops penetrated the city Monday, members of Saddam's Fedayeen paramilitary fighters prevented journalists from leaving the Palestine Hotel, where many were staying.

Iraqi troops did not use any mortars or artillery against the American forces.

F-16 fighter jets flew ahead of the U.S. armored column, bombing any tanks or armored personnel carriers along the way. U.S. troops also fired mortars on key intersections before passing through. Tanks took up positions around key intersections.

Black smoke clogged the air and covered the city.

The assault on Baghdad followed a weekend of incursions by U.S. forces in tanks and armored personnel carriers. Troops rolled through streets of the capital "destroying all of the enemy vehicles and personnel with whom they've come in contact," Gen. Peter Pace, vice chairman of the Joint Chiefs of Staff, told CNN on Sunday.

"One of the points is to destroy the enemy that we found, and the last two raids have been very, very successful at doing that," he said.

Intermittent explosions were heard in the city Sunday night into Monday, along with periodic anti-aircraft fire. Shortly before dawn, aircraft could be heard over the capital and heavier explosions shook downtown buildings, echoing from the southern outskirts.

After sunrise, a long series of blasts rocked Baghdad and dark gray smoke rose on the horizon to the south and southwest. Residents could hear what seemed to be the sound of surface-to-surface rockets, artillery and aircraft.

Prayers broadcast from Baghdad's mosques filtered through the din of battle. "God is great and to him we owe thanks," clerics intoned every time the city came under attack.

South of the capital, U.S. forces took control of the center of the holy city of Karbala on Sunday after block-by-block fighting, the Army Times newspaper reported from the scene.

Suggesting disarray among Iraq's elite fighters, Iraqi President Saddam Hussein urged Iraqi troops separated from their combat units to join other squads to fend off the Americans, in a statement read Sunday on Iraqi television and radio.

The statement also said anyone who destroys an allied tank, armored personnel carrier or artillery would be awarded 15 million dinars, or about $8,000 by the unofficial exchange rate.

Iraqi satellite television showed brief footage of a smiling Saddam in military uniform chairing a meeting it said was held Sunday with his top aides.

In a separate announcement, a broadcaster for Iraqi state radio read a decree by Saddam that two female suicide bombers be awarded posthumously the medal of the Al-Rafdin -- or "The Two Rivers" -- the nation's highest decoration, and that their families be given 50 million dinars or about $28,000 each.

The attack last week in western Iraq killed three U.S. soldiers at a checkpoint 80 miles from the Syrian border.