British Prime Minister David Cameron unveiled Thursday new measures to end the country's worst riots in decades, and admitted that the government could call in the army to quell the violence.

As a police crackdown and heavy rain prevented a fifth night of chaos, Cameron told an emergency session of parliament he would give police extra powers including the ability to order youths to remove face coverings.

Cameron said that a year before London hosts the 2012 Olympics, Britain needed to show a more positive face to the world after the riots in which four people have died and dozens of buildings have been torched.

"We will not stop until this mindless violence and thuggery is defeated and law and order is fully restored on all our streets," he told lawmakers.

"We need to show the world, which has looked on frankly appalled, that the perpetrators of the violence we have seen on our streets are not in any way representative of our country -- nor of our young people."

Anyone whose property was damaged will be compensated, Cameron added.

Britain is still reeling after four of the worst nights of rioting for decades, which started in London then spread to other English cities including Manchester and Birmingham.

The riots started on Saturday, sparked by anger over the shooting by police of a 29-year-old man, Mark Duggan, in the deprived north London district of Tottenham.

Cameron, who cut short his holiday to deal with the crisis, said initially that "simply far too few police were deployed onto the streets".

Police had treated it as a public order situation instead of criminality, he said.

But he disclosed for the first time that he and senior security officials had discussed calling out the military to help, and said they were examining the possibility that curfews could be used to curb future violence.

"It is my responsibility to make sure that every contingency is looked at - including whether there are tasks that the army could undertake that would free up more police for the front line," he said.

Those included "some simple guarding tasks" but he added this was "not for today, it is not even for tomorrow, it is just so you have contingency plans in case it becomes necessary".

He reiterated that police had been given powers to use water cannon and plastic bullets, and also suggested they use technology to control future unrest, by stopping rioters using Twitter, Facebook or BlackBerry Messenger to organise themselves.

Cameron, whose Conservative-led coalition government is bringing in tough spending cuts, also dismissed claims that poverty had contributed to the unrest, saying it was "not about politics or protest, it is about theft".

He said there was evidence that "street gangs" had coordinated attacks on police and looting, adding that he wanted Britain to follow the record of US cities like Boston in tackling gang violence.

Police started raiding addresses in London on Thursday to arrest people involved in the violence.

Courts meanwhile stayed open overnight to deal with a backlog of more than 1,200 people arrested during the riots. Several people received jail sentences on Thursday while others were bailed.

Those facing judges have included an 11-year-old girl who admitted criminal damage in the central English city of Nottingham, a 17-year-old dancer, a chef, a teaching assistant, an opera steward and an army recruit.

In Birmingham, the father of one of three Muslim Asian men who died in a hit-and-run incident emerged as a heroic figure for his impassioned calls for peace despite the spectre of inter-racial tensions.

Tariq Jahan, whose 21-year-old son Haroon Jahan was one of those killed, was featured on the front page of several newspapers addressing an angry crowd and urging them not to take revenge.

"I lost my son. Blacks, Asians, whites - we all live in the same community. Why do we have to kill one another? Why are we doing this? Step forward if you want to lose your sons. Otherwise, calm down and go home - please," he said.

Police on Thursday arrested three suspects aged 16, 17 and 26 following the incident while a 32-year-old man arrested on suspicion of murder on Wednesday was bailed.

Meanwhile Malaysian student Asyraf Haziq Rosli, 20, who was mugged during the riots by a group of youths who pretended to help him after he suffered a broken jaw, left hospital in London on Thursday.

Footage of his ordeal has been watched by thousands of people on the Internet.

Scotland Yard are making Rosli's case a priority because the video of his attack has come to epitomise the violence for many people, one officer said.

The English Premier League said Tottenham's opening match of the season against Everton had been postponed because of the violence but that so far the nine other fixtures due to take place this weekend would go ahead as planned.