Inhabitants of Falluja are returning to their homes for the first time since the American-led assault on insurgents left much of the Iraqi city in ruins.
Residents ignore warnings about clashes and unexploded mines
An initial group of 2,000 is being allowed in to inspect their homes, and decide if they want to stay.
Most of Falluja's population of about 250,000 fled November's fighting.
As residents waited, explosions shook the area followed by a huge plume of smoke. Iraqi authorities say people insist on returning despite the risks.
There are continuing clashes and unexploded mines in the streets of the city, they say.
In other developments in Iraq:
- More than 40 suspected Iraqi
insurgents are arrested by US marines during a series of raids in towns south of Baghdad
- A policeman is killed in a missile attack on a Baghdad police station
- The police chief in the volatile al-Anbar province of western Iraq resigns after gunmen tried to kill him, the province's governor says
- An American company involved in building projects in Iraq, Contrack International, announces it is withdrawing because of the level of violence and rising security costs.
At US checkpoints, returning men of military age are being fingerprinted and having their irises scanned to try to ensure that no insurgents return.
An eyewitness said some of the first citizens to re-enter the city reportedly did so in their private cars, after being given badges clearing them to enter their houses in the Andalus neighbourhood.
Andalus, in the west of the city, is said to have seen less destruction than other neighbourhoods.
And east of the city, about 100 people lined up at an Iraqi
National Guard checkpoint to receive passes giving them permission
American military officials have acknowledged that returning residents will be shocked by the state of their city.
A spokesman for the US marines said Falluja was not yet ready for what he called comfortable living. As well as the continuing clashes and remaining mines, there is still no running water or electricity, and the rubble of destroyed buildings has not yet been cleared.
However, the BBC's Caroline Hawley in the Iraqi capital, Baghdad, says civilians who fled the city to neighbouring areas are now desperate to return.
Many have been camping out in winter temperatures in tents, or staying in schools and other public buildings.
National Security Minister Kassim Daoud told reporters: "We have told them that there are areas where the debris has
not been removed so far, there are homes that are destroyed,
there are mines in some streets, but our people insisted that
they want to return to their city."
The 2,000 people being allowed back on Thursday are part of a staged return that is expected to last a few weeks.
US officials acknowledge that returnees will be shocked
The government says it has set up water tanks for them in the city, and will give each returning resident $100.
It is also promising eventually to pay compensation to the many whose homes have been destroyed or damaged.
Mr Daoud said there was still sporadic fighting in some areas.
"But that doesn't mean there is a huge amount of resistance. It is just people coming in from neighbouring areas to carry out some attacks," he added.