Iraqis expressed joy at the news that US forces had completed their withdrawal on Sunday, but voiced doubts their politicians could come together to rebuild the violence-wracked country.

Their lack of confidence in their leaders was highlighted by renewed political crisis as Prime Minister Nuri al-Maliki sought to oust one of his deputies and the main Sunni-backed political bloc boycotted parliament, just as the final US troops crossed into Kuwait to end the nearly nine-year war.

As news of the pullout reached Baghdad, the streets of the Iraqi capital and other major cities were little changed, with heavy commuter traffic snaking through police and military checkpoints.

"I am proud -- all Iraqis should be proud, like all those whose country has been freed," 26-year-old baker Safa, who did not want to give his real name, told AFP in Baghdad's Karrada commercial district. "The Americans toppled Saddam, but our lives since then have gone backward.

"The situation will only improve if politicians work on fighting corruption and adopt reforms," he added.

Sunday's completion of the withdrawal brings to a close nearly nine years of American military involvement in Iraq, beginning with a "shock and awe" campaign in 2003 to oust Saddam, which many in Washington believed would see US forces conclude their mission in Iraq within months.

But key decisions taken at the time have since been widely criticised as fuelling what became a bloody Sunni Arab insurgency, eventually sparking devastating communal violence.

"I don't think we can ever forgive the Americans for what they did to us, from killings to terrorism," said a 50-year-old mother-of-four who gave her name only as Umm Mohammed, or mother of Mohammed.

"Those people (Americans) think only about themselves, and not about the consequences of their actions."

More than 100,000 Iraqis have been reported killed in violence since the invasion, according to British NGO Iraq Body Count, and countless others were wounded.

In the mostly Sunni Arab north Baghdad neighbourhood of Adhamiyah, where Saddam Hussein was last seen publicly before his capture, 60-year-old retiree Mohammed Abdelamir said he felt "freed from the occupation," referring to US troops as many Iraqis long have, as an occupying force.

"We must all cooperate and work to improve the economy, the society, and begin rebuilding, and not fight because we are seeing that some politicians have already begun putting a stick in the wheel."

He was referring to signs of unravelling in Iraq's year-old national unity government which emerged just as US forces completed their withdrawal.

On Sunday, Maliki conveyed an official message to parliament, calling on lawmakers to oust his deputy Saleh al-Mutlak, a Sunni Arab and member of the secular Sunni-backed Iraqiya bloc.

A day earlier, Iraqiya said it was boycotting parliament in protest at the premier's alleged centralisation of power. It has not, however, withdrawn from the government.

Key political issues such as reform of the mostly state-run economy and a law to regulate and organise the lucrative energy sector also remain unresolved, to say nothing of an explosive territorial dispute between Arabs and Kurds centred around the northern oil hub of Kirkuk.

"Today is a historic day, and our happiness is great," said Abdul Hussein Hosh, a 59-year-old government employee in the sprawling Baghdad Shiite district of Sadr City.

"But what makes us sad is that this occasion came at a time when Iraqiya announced they were withdrawing. ... This shouldn't have happened when the occupier was leaving our country."

Some observers also fear a return to bloody sectarianism, doubt the strength of Iraq's political structures, and feel that Maliki has entrenched his power base to the detriment of the country's minorities.

"Today marks the first day of danger for Iraqis," said Roudi Slewah, a 25-year-old Christian shop owner in multi-ethnic Kirkuk. "We didn't want the Americans to stay in Iraq, but the region could explode at any time.

"The danger starts from today," he said.