"There were at least 13 casualties and one soldier killed in action," said First Sergeant Jeff Treiber.





The marines 1st Division, 5th Regiment have captured one of Saddam's main palace complexes on the northern side of the Tigris, said Treiber, of the regiment's 1st battalion.





The marines were under fire since 2.00 am (2200 GMT on Wednesday) from fighters hiding in buildings, in cars, on rooftops and beneath bridges, an AFP correspondent on the ground saw.





Heavy fighting was still raging with Iraqi fighters using AK-47s and rocket-propelled grenades, the correspondent said.





"It's a show of force, we can go where we want," said Treiber, adding that artillery fire could be heard outside the walls of Saddam Hussein's Azmiyah palace.





Major Pete Farnum also said a nearby mosque had been secured.





"There were intelligence reports the mosque was a Saddam stronghold," Farnum said, describing the mosque as being close to the northern banks of the Tigris.





"We displayed our ability to impose our will," he said, in reference to the marines capturing the mosque and palace.





A BBC correspondent said US troops had searched the mosque, where Saddam Hussein was rumoured to be hiding.





Earlier a series of loud blasts woke Baghdadis on Thursday in a sharp reminder of the dangers still lurking in Iraq after the euphoria of the fall of the capital to US forces.





The booms from the outskirts were heard clearly from 7:30 am (0330 GMT) while planes could be heard flying overhead, an AFP correspondent reported.





The city centre was calm in the morning as it had been throughout the night for the first time since the war began on March 20.





But the uncertainty of the situation was reflected by the explosions which could not be immediately located and it was unclear if they were the result of airstrikes.





US forces seized control of most of Baghdad on Wednesday and met surprisingly little resistance.





Jubilant crowds turned out to greet them as Saddam Hussein's regime collapsed as quickly as the American armour push into the heart of the city.





The world watched live the chaotic scenes as Iraqis waged a symbolic struggle to topple a huge statue of Saddam in a central square.








However, the war is still raging, military and political leaders warned as sniper fire rang out intermittently in the capital.





A sniper shot dead a US marine in southeastern Baghdad on Wednesday, US Central Command said.





A series of massive explosions had lit up the sky during the evening on Baghdad's southwestern rim.





In central Baghdad, a Belgian doctor, Geert Van Moorter, said two Iraqis were killed and three others wounded when US forces opened fire on an ambulance carrying away people injured in exchanges of fire.





An AFP reporter also saw a convoy of marines come under fire after the lead vehicle was rammed by an Iraqi car on Baghdad's eastern outskirts.





Saddam's hometown of Tikirt in the north was still under bombardment and cited widely as a likely last refuge for the ousted rulers. And the major northern cities of Kirkuk and Mosul are still in the hands of the regime.





"We are still in the midst of a shooting war and men and women are still in harm's way ... There remain a lot of dangers ahead," said White House spokesman Ari Fleischer.





"This conflict is not, however, over yet," added British Prime Minister Tony Blair.





"We control the vast majority of the city but there's still fighting going on," cautioned Lieutenant General Buford Blount, commander of the Third Infantry Division, said at the airport where US forces are based.





After three weeks of war, US troops had faced only sporadic gunfire as they moved up both banks of the Tigris river that divides the city to the applause of hundreds of civilians, some of them chanting, "Good, Good, Bush!", while others indulged in widespread looting.





Iraqi Information Minister Mohammad Said al-Sahhaf, who gave daily briefings denying any advance by US-led forces, and other officials were nowhere to be seen.





Nothing has been heard from Saddam since a US B1 bomber flattened a building he was believed to have entered in the Al-Mansur district on Monday.





"He's not been around. He's not active. Therefore, he's dead, or he's incapacitated or he's healthy and he's cowering in some tunnel someplace trying to avoid being caught," US Defense Secretary Donald Rumsfeld said in Washington.





In London, newspapers quoted intelligence sources as saying Saddam had likely left just before, maintaining his reputation for secrecy and survival built up over decades.





There was also 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.





But Rumsfeld dismissed talk of a humanitarian crisis and said aircraft delivering aid supplies had already landed at Baghdad airport.