The suicide bombing "happened north of here," Major Matt Baker of the US Marines told AFP 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 and 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 city 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 the city slipped further into chaos.

The buildings housing the ministries of information, trade, education, higher education and industry were ablaze, as was the old market of Baghdad's commercial center on Rashid Street.

No firefighters or US marines were in sight to extinguish the flames.

The skyline of the capital glowed orange as clouds of smoke billowed into the night air.

Much of the city has been without power for days and plunged into total darkness after dusk.

The Republic Bridge over the Tigris River, which divides the city in two, was blocked by burning cars, and the few terrified pedestrians on the street asked how they could cross the river to get home.

The key bridge in the heart of the city had been the site of countless firefights between US forces on the western bank of the river, near Saddam Hussein's main presidential palace, and Iraqi fighters on the eastern side.

But the last defenders of the regime abandoned their posts Wednesday.

As darkness fell over the city center on the eastern bank Thursday, roving bands ran amok.

Teenagers and old men alike sacked the area street by street after the city's conquest by US forces lifted the last restraints, targeting official buildings, state-run shops and the luxury villas belonging to President Saddam Hussein's inner circle, including his elder son Uday and daughter Hala.

Buildings that had once inspired fear, such as the headquarters of the air force and the regime's formidable security apparatus, also fell prey to looters.

But sites such as hospitals and offices of the Iraqi Red Crescent were not immune, as bandits walked off with beds, operating tables and surgical instruments.

Looters also turned their attention to the German embassy and the French cultural center.

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 bank 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-off 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 had 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.

There was concern about the humanitarian situation after the International Committee of the Red Cross suspended aid deliveries in Baghdad, following the death of a Canadian staff member in crossfire Tuesday.

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.

SPACE.WIRE