British police are being given the leeway to use any measures they deem appropriate to quell the rioting that has beset London and other English cities in recent days.

Standing in front of his Downing Street office on Wednesday, Prime Minister David Cameron said the police have the full support of the government as they seek to dismantle the "groups of thugs" who have terrorized Britons by burning down buildings and looting shops at will.

"Whatever resources the police need, they will get. Whatever tactics the police feel they need to employ, they will have legal backing to do so," said Cameron, who plans to hold an emergency debate in Parliament on Thursday regarding the riots.

"We will do whatever is necessary to restore law and order onto our streets," he said.

The prime minister's words came the morning after London saw its first night of relative peace after three straight evenings of looting and rioting in neighbourhoods across the capital. But the violence continued to spread to other parts of the country overnight Tuesday, particularly western and northern England.

Police flooded the streets of London for a second consecutive night Wednesday. Quiet prevailed on the streets again, after 16,000 officers deployed Tuesday evening appeared to deter further rioting.

But in Birmingham, racial tensions flared Wednesday after three south Asian men were killed by a vehicle that reportedly had a black driver.

Tariq Jahan, whose 21-year-old son Haroon was killed in the incident, pleaded with the city's South Asian community not to seek revenge for the deaths.

"Today we stand here to plead with all the youth to remain calm, for our community to stand united," he said from the street. "This is not a race issue. The family has received messages of sympathy and support from all parts of the community -- all races, all faiths and backgrounds."

The men who died were believed to be patrolling their neighbourhood to fend off looters. Police said a man has been arrested on suspicion of murder in connection with the case.

The information investigators have gathered so far suggests that "the car was deliberately driven," said Chris Sims, chief constable of West Midlands Police.

"My concern would be that that single incident doesn't lead to a much wider level of distress and even violence between different communities," he added.

Police ‘fightback'

More than 800 people have been arrested in connection with the unrest in the capital alone. Holding cells in London were completely filled up, forcing police to ship newly arrested suspects to jails elsewhere.

Five hundred detectives are involved in investigating their suspected crimes and laying charges against them.

"That is more detectives than were assigned even to investigate the terrorism of 2005 in London," CTV's London Bureau Chief Tom Kennedy reported Wednesday. "It's the biggest single investigation in the police force's history."

Meanwhile in Manchester, Garry Shewan, the assistant chief constable of the local police force, suggested that the rioters there were engaging in criminal acts for no definable reason.

Hundreds of youth ran amok in the northwestern city Tuesday night, throwing stones at police, vandalizing stores and lighting a women's clothing store and a library on fire.

Rioters in the central city of Nottingham threw a firebomb through a police station window Tuesday night and set fire to a school and a vehicle. Ninety people were arrested by the end of the night.

Police also tangled with rioters in Liverpool, Leicester, Wolverhampton, West Bromwich, Bristol and Gloucester.

When Cameron made his remarks Wednesday, he urged Britons not to lump all young people in with the rioters and said those who participated in the disturbances belonged to "pockets of our society that are not just broken, but frankly sick."

However, the violence has reignited debate over the Conservative-led government's planned budget cuts, which aim to remove 80 billion pounds ($130 billion) from public spending over the next four years.

Riots bring calls for vigilantism, also clean-up

The repeated riots also drew responses from some groups that intended to take policing-type duties up themselves.

One far-right group said about 1,000 of its members would take to the streets on Tuesday to deter would-be rioters.

"We're going to stop the riots -- police obviously can't handle it," said Stephen Lennon, the leader of the far-right English Defence League, in an interview with The Associated Press.

Other people took to the streets after the riots to help clean up the mess.

Many ordinary Britons organized clean up efforts through Twitter and other social media, bringing brooms and a sense of civic responsibility back to the streets.

But the riots have also brought Britain bad publicity in the lead-up to next year's Olympic Games, which are going to take place in London.

"There are people who say: ‘Well we should just bring in the army,'" Globe and Mail correspondent Doug Saunders reported Wednesday.

"I suspect that Prime Minister David Cameron is very reluctant to do that only months before London hosts the Olympic Games, to have scenes of an Iraq-style military occupation in his own capital city filling the TV screens of the world."

With files from The Associated Press