An AFP correspondent said the streets were calm and that five armored vehicles were in the centre of the city, which appeared to have been deserted by Iraqi regular forces and much of the population.

A handful of people stepped from their homes to catch a glimpse of US troops, who were preparing for intense fighting in the city, Saddam's hometown and a traditional stronghold of his Baath party.

The fall of Tikrit, the last major Iraqi city not yet in the hands of US-led coalition forces, would essentially signal the end of the war launched by the United States and Britain on March 20 to topple Saddam.

A sergeant said three US marine reconaissance battalions entered before dawn, meeting no resistance.

Sergeant Robert Chute said: "My feeling is this means the end of the war.

"We didn't encounter any resistance in the city, but only on the outskirts last night. We had bad ambushes there."

Firefights with what Chute believed to be Iraqi soldiers had left at least one Iraqi dead, while US units reported no wounded or dead.

"I thought they were Iraqi soldiers because we found some RPGs (rocket-propelled grenades) there. We had no casualties," the sergeant said.

US Central Command downplayed any talk that Saddam's tribal stronghold 180 kilometres (115 miles) north of Baghdad had fallen and said there remained some Saddam loyalists who had not given up the fight.

"There are still some operations to be done in Tikrit, there are some regime forces that are still in the area and that haven't surrendered yet," said Lieutenant Herbert Josey, a spokesman at the Command's base in Qatar.

Outside the centre of Tikrit, witnesses reported gunfire as residents warded off looters, but there was no immediate confirmation of the report.

US troops aboard four helicopters landed near the Tikrit headquarters of Saddam's Fedayeen militia but encountered no resistance, witnesses said.

Tribal chiefs had sought to negotiate a peaceful entry by coalition troops, but intermittent air strikes could be heard on the city's outskirts throughout the night.

A Canadian journalist with the US marines, Matthew Fisher, told CNN that the 250 US armoured vehicles which entered the city had met some resistance from loyalist forces.

He quoted US commander John Kelly as saying five Iraqi tanks had been destroyed on the outskirts of the city and at least 15 people killed in firefights.

However the fighting fell well short of the feared last stand by Saddam's closest tribal allies.

Meanwhile in Baghdad, US troops were trying to maintain some order in the chaotic city, wracked by days of looting since Saddam's 24-year grip on the Iraqi capital collapsed last week.

But there were still sporadic bursts of fighting. Marines exchanged fire with unidentified targets around the Palestine Hotel in central Baghdad overnight, AFP journalists in the capital reported.

The marines occasionally opened fire with automatic weapons and fired flares around the hotel, which houses most foreign media in the Iraqi capital, they said, after what had been an otherwise relatively calm Sunday.

A US military spokesman said US troops would start joint patrols with Iraqi security forces. US officials have begun trying to rebuild the Iraqi police force as well as drawing people back to key sectors such as the electricity department.

US forces on Sunday retrieved seven POWs who had been held since March 23. Five had been taken in an ambush and two others were pilots of an Apache helicopter which had been downed the same day.

"They were all in great condition, great spirits. A few injuries, nothing major," said Lieutenant Colonel Ruth Lee, a nurse who saw several of the former captives at an undisclosed military location in Kuwait on Sunday.

US General Tommy Franks, who is commanding the war on Iraq, said the United States had samples of Saddam's DNA and that forensic tests would be under way to see if the long-elusive Iraqi leader had been killed in a massive Baghdad air strike.

In the main northern cities of Mosul and Kirkuk, calm had returned Sunday after two days of looting and intercommunal fighting, with US troops reassuring Turkey by replacing Kurdish fighters in the oil-rich cities.

Mosul police were back on the streets while vigilantes were also trying to restore order in the city of 1.5 million, where as many as 20 people were killed and 200 wounded in two days of fighting between Arabs and Kurds.

Kurdish residents and members of the Free Iraqi Forces -- part of the US-backed Iraqi National Congress (INC) umbrella opposition group -- were sharing the task of protecting the city's infrastructure, US military sources said.

The situation was similar in Kirkuk, the other northern oil hub, where calm was slowly returning to the streets.

In the south, British troops were beginning joint police patrols with Iraqis in the city of Al-Faw, a reporter said.

burs-mc/wai

SPACE.WIRE