Civilians interviewed in the city's center said they wanted to surrender to US forces as long as these were not accompanied by Iraqi opponents of Saddam Hussein, who had his power base in the northern city.

Residents carrying assault rifles and grenades said they needed to protect themselves against looters, but a live broadcast showed that gunmen fired on a CNN crew after they refused to stop at a checkpoint while leaving the city.

Saying that much of the population had fled Tikrit, the inhabitants asked journalists to report they were ready to surrender and that Tikrit would not resist.

The city was extremely tense, however.

US marines, who left Baghdad earlier, were closing in on Tikrit, according to a military spokesman at the Central Command headquarters in Qatar.

"Task Force Tripoli has moved north and is currently conducting operations in the vicinity of Tikrit," said Captain Frank Thorp, adding: "It is a significant force, it has got significant firepower."

Tikrit and other parts of the north where remnants of Iraqi forces put up fierce resistance are now the main target of coalition forces, according to officials at the US war command center.

The road into Tikrit from the northern city of Mosul was open Sunday, but had not been secured by coalition troops, an AFP correspondent said.

CNN showed pictures of abandonned barracks of the Republican Guard outside the city.

The area had been the target of more than one week of intense bombing, but it was not clear when US forces would seek to enter the city.

Tikrit is considered the last major city not under control of the coalition forces, though Centcom officials say operations are focused on populated areas in a vast area stretching north of Baghdad and south of Kirkuk.

"A lot of populated areas still have a regime presence," said Major Rumi Nielson-Green.

She said remnants of decimated Republican Guard units had banded together to fight coalition troops.

"Those fights are significant and fierce," she said, adding, however, that the Iraqi units were "just mismatched leftovers with no military command and control".

In southern Iraq, the US-led forces were engaged in mop-up operations, she said.

US marines "entered Al Kut unopposed, they were assisted by contacts with local leaders," said Thorp.

In Basra, Iraq's second largest city, British army engineers brought in earth-moving equipment after locals claimed prisoners were trapped in cells underneath the main police station.

In Baghdad, US forces tried to restore normalcy after days of looting in the battered city.

They set up an operations center to screen Iraqi workers in the heart of the city, where hundreds of locals lined up for jobs in the post-Saddam Hussein era.

A marines spokeswoman said US forces were seeking to put Iraqis back at work in key sectors, starting with the police and electrical power departments.

On Saturday, a marine was shot dead at a checkpoint outside a Baghdad clinic and one of the attackers, who carried a Syrian identity card, was also killed, according to Centcom.

Marines on Friday found more than 300 vests fitted for use by suicide bombers, it added.

In the northern city of Mosul, stretched US special forces turned to police officers of the ousted regime to stem ethnic clashes that have killed as many as 20 people.

The move threatened to complicate the US force's relations with Kurdish rebel allies who entered the city without a fight on Friday and for whom the mainly Sunni Arab police are a hated symbol of the old regime.

Meanwhile, peace began to return to Kirkuk following two days of looting after Kurdish peshmerga fighters seized the city almost unopposed on Thursday.

US soldiers began to arrive in the city on Friday after Turkey, which fears Kurdish dominance of the north would arouse separatist aspirations among its own Kurdish minority, secured a pledge from Washington to force the peshmergas out.

In western Iraq, an influential tribe has said it was trying to negotiate a deal with other leaders in a bid to allow coalition forces to peacefully enter the province of Anbar, according to Al-Jazeera television.

The mostly desert province, which borders Jordan to the west, has been largely bypassed by the war apart from an early move by coalition special forces to secure two air bases seen as a threat by Israel.

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