British soldiers have offered a gun amnesty in Basra in an effort to restore order to the southern Iraqi city.
Basra residents celebrating on hearing about the fall of Baghdad
The troops say they have been largely successful in stamping out the looting which has dogged the city in the two days since they entered it.
But the large number of weapons in circulation was still a cause for concern, they said.
Reporters said Basra had calmed down on Wednesday, but there was still sporadic looting and arson attacks.
Reports of the fall of Baghdad were met by scenes of singing, dancing and chanting.
Young men huddling around radios jumped on the spot and ran down the street, arms aloft in celebration, said one reporter.
British forces said they had begun working with remnants of the police force and community leaders to try to restore order.
Warehouses holding humanitarian aid like sugar have been raided
But residents complained of a power vacuum and continued lawlessness.
"No authority now. No law now. No anything. Thieves
everywhere," said one man.
In one episode soldiers had to prevent a raid on a bank vault.
Local reports said one man had died in a fire which broke out as a mob tried to loot the building.
"We have been given nothing for 30 years," shouted one Basra resident. "This is our
Residents have also reportedly been storming warehouses where UN humanitarian supplies of sugar and soap were held.
Another Iraqi was reportedly stoned to death by locals for stealing goods from shops.
UK troops have been concentrating on tackling the last opposition fighters rather than keeping law and order, said the BBC's Clive Myrie, in southern Iraq.
Until the security situation is improved, humanitarian aid cannot be brought in.
The commander of the UK forces in the Gulf, Air Marshal Brian Burridge, said he hoped a full-scale humanitarian aid effort could be launched within several days.
Doctors in Basra's main teaching hospital told our correspondent they had only about two weeks of medicine left.
Water and electricity are also in short supply in the city.
Coalition forces said they were planning to hold a regional conference soon to establish political leadership for the whole of southern Iraq.
The delegates would be drawn from local leadership committees across the region - and may also include leading opposition figures from abroad.
Residents of Basra are being urged to dump their guns in an "amnesty pit" close to one British military compounds.
"Iraq has a culture of weapons. There are a lot of them around, most held
quite legally," said Captain Cliff Dare, of 3 Commando Brigade Engineer Group.
"If we want to give the new Iraq a chance these weapons have to be taken out
Elsewhere, British forces in southern Iraq have made their furthest advance north and crossed the River Euphrates, with the 1st Battalion Royal Irish Regiment reaching al-Qurnah.
A group of newly-arrived American marines are advancing east across Iraq as a prelude to securing another supply route from Basra to Baghdad, the BBC's David Loyn said.
The marines are said to be outside Amara in southern Iraq and are close to linking up with British formations.