A suicide bombing in Baghdad killed at least one US soldier Thursday, after marines came under heavy fire from pro-regime pockets of resistance.
"It happened north of here," Major Matt Baker of the US Marines said at the Palestine Hotel in the heart of the city where the foreign press is staying.
A US military source said the attack had taken place in Saddam City, an impoverished suburb in the north of Baghdad home to two million people, mostly Shiite Muslims.
It was the first suicide attack against American forces since they captured Baghdad amid scenes of jubilation and looting Wednesday, and raised fresh doubts about how firmly coalition forces held the capital in their grip.
The incident was the third such assault against troops of the US-British coalition since the war began March 20 and came after the assassination earlier Thursday of pro-Western Iraqi Shiite leader Abdul Majid al-Khoei in the holy city of Najaf in central Iraq.
On Thursday evening, at least five ministries were on fire in downtown Baghdad as looters rampaged through the Iraqi capital where anarchy was setting in.
Earlier in the day, Iraqis pillaged the deserted luxury homes of senior figures of Saddam Hussein's regime, including his maverick son Uday.
After the initial euphoria of the fall of Baghdad, looters also turned their attention to the German embassy and the French cultural centre.
In a further stark reminder that not everyone in Baghdad was pleased to see US troops in the city, marines were earlier attacked by forces loyal to Saddam along the northern banks of the Tigris river.
One marine died and 20 were wounded in the exchange at a mosque and a presidential palace complex after receiving a tip that Saddam himself was inside, said Major Rod Legowski, liaison officer of the 3rd Infantry Division (3ID).
"That's what we were told. That's why we went after those targets - Saddam and other top level officials," Legowski said.
Five Iraqi civilians were also killed in the firefight, witnesses said.
US combat helicopters came to the aid of soldiers on the ground battling Iraqi and Arab fighters in a district of central Baghdad.
Five Apache helicopters hovered for over an hour over Al-Kadhimia and Al-Otayfia neighborhoods, on the west bank of the Tigris as well as Al-Aadhamia on the opposite side.
The clashes pitted US troops against Fedayeen paramilitary units and Arab volunteer fighters hiding behind sandbag reinforcements on street corners in Al-Otayfia.
In the southwestern district of Al-Dora, dozens of bodies, including those of children, and burnt-out cars littered the streets.
The putrid, fly-covered corpses were being buried along the sides of the road by volunteers.
A US officer at the scene said Fedayeen fighters attacked an American convoy which retaliated, causing the deaths. But witnesses said US soldiers opened fire on cars carrying civilians they thought posed a threat.
Baghdadis were awoken Thursday to a series of loud blasts on the city's outskirts around 7:30 am (0330 GMT) while US planes roared overhead.
The night, however, was quiet for the first time since the war to oust Saddam's regime began on March 20.
In the Jadria and Hay Babel areas on the eastern bank of the Tigris, the villas of Deputy Prime Minister Tareq Aziz, Saddam's daughter Hala, his half-brother Watban, and army generals, were systematically ransacked.
Uday's villa was totally stripped except for a fixed wrought iron barbecue in the middle of the garden.
A truck outside Uday's house was laden with a huge oak table and gold chairs, while a painting of Saddam was left abandoned on the ground.
Around midday, a US army unit that had been stationed overnight at Aziz's home joked with a group of around 20 looters who feverishly waited outside to ransack the house.
As soon as the Americans left, the group rushed in to grab anything that came to hand. US soldiers said the furniture inside the house had been left covered with sheets, as if the owner had been planning to return.
Gun-toting looters, meanwhile, stole two ambulances and medicine from Al-Kindi hospital, one of Baghdad's leading civilian treatment centres.
US troops called to assist said they had no orders to intervene.
Two American troop transporters and a dozen men, however, have been deployed outside the headquarters of the International Committee of the Red Cross (ICRC) in the Iraqi capital.
There was concern about the humanitarian situation after the Red Cross suspended aid deliveries in Baghdad, following the death of a Canadian staff member in crossfire Tuesday.
US forces seized control of most of Baghdad Wednesday and met surprisingly little resistance.
US Marines used a tank recovery vehicle to bring down the towering statue of Saddam over Al-Fardus (Paradise) Square.
On Thursday, a white-bearded man in his sixties carefully placed the bronze, lopped-off head of his former leader in a wheelbarrow.
"I have dreamed of this day for years," he said.
Nothing has been heard from Saddam since a US B1 bomber flattened a building he was believed to have entered in the upmarket Al-Mansur district of the capital on Monday.