British Prime Minister David Cameron vowed Wednesday to do "whatever is necessary" to halt massive riots that have swept London and other major cities in recent days — the worst such violence to hit the country in decades.
A wave of arson and looting that started in parts of London on Saturday has spread to other cities, including Manchester and Birmingham.
Cameron, who has recalled Parliament from its summer recess for an emergency debate on the riots, said police have drawn up contingency plans to "do whatever is necessary to restore law and order onto our streets.
"Nothing is off the table," the prime minister said in a somber television address.
Scenes of ransacked stores, torched cars and blackened buildings have frightened and outraged Britons just a year before their country is to host the Summer Olympics. In London, where armored vehicles and convoys of police vans patrolled the streets, authorities said there were 16,000 officers on duty — almost triple the number present Monday night.
Almost 800 people have been arrested in the capital alone and 400 more in other cities since the violence began.
The diverse working-class borough of Hackney in North London, which had been a focal point for the looting and chaos, was quiet Tuesday night along with the rest of the city. Hundreds of shops were shuttered or boarded up as a precaution.
Thousands of extra officers from outside London, including 100 from Manchester, helped secure Hackney and other boroughs. Several dozen police vans packed with officers swarmed the area, stopping just about any young person on the street.
"I think the worst is over," Hackey resident Andy Wager told NPR. "I think now it's just little bits here and there. I think the police have it under control in London. I don't know about other places, though."
Outside the capital, some looting erupted, but not on the scale of the violence that hit several areas of London on Monday night.
About 250 people were arrested after two days of violence in Birmingham, where police launched a murder investigation after the deaths of three men hit by a car.
Some residents said the dead men, ages 20 to 31, were members of Birmingham's South Asian community who had been patrolling their neighborhood to keep it safe from looters.
Chris Sims, chief constable of West Midlands Police, said a man had been arrested on suspicion of murder in the case.
"The information we have at the moment would support the idea that the car was deliberately driven," he said, appealing for calm. "My concern would be that that single incident doesn't lead to a much wider level of distress and even violence between different communities."
Britain's riots began Saturday when an initially peaceful protest over a police shooting of a black man in London's Tottenham neighborhood turned violent. Initially, rioters were left virtually unchallenged in several neighborhoods, and when police did arrive the rioters often were able to flee quickly and regroup.
In the northwestern city of Manchester, hundreds of youths rampaged through the city center, hurling bottles and stones at police and vandalizing stores. A women's clothing store on the city's main shopping street was set ablaze, along with a disused library in nearby Salford.
Manchester Assistant Chief Constable Garry Shewan said the actions were simple lawlessness.
"We want to make it absolutely clear — they have nothing to protest against," he said. "There is nothing in a sense of injustice and there has been no spark that has led to this."
But others have blamed the violence on growing disparities in wealth and opportunity in Britain, which have been worsened by austerity cuts and a flagging economy.
"I do think it is about the divide between those who have opportunity and strongly perceive they have them and those who worry that they don't," said Mike Hardy, who directs the Institute of Community Cohesion, a think tank at the University of Coventry.
But David Lammy, a member of Parliament from Tottenham, told NPR that "politicians have to be really, really careful about the excuses they are playing into this story," although he acknowledged the "very difficult economic backdrop" to the violence.
"We are seeing not retail chains, but independent shops — hairdressers, travel agents, post offices — burnt to the ground," he said. "I'm afraid there will be profound questions about what has happened with a particular constituency of young people that their values are such that they could steal, rob and endanger life in their own neighborhood in this way."
Lammy said it was "deeply worrying that the police are being outfoxed by these young people, using Twitter and using their BlackBerry messengers to move to other areas and get there long before the police can catch up with them."
Some residents stood guard to protect their neighborhoods. Outside a Sikh temple in Southall, West London, residents vowed to defend their place of worship. Another group marched through Enfield, in North London, aiming to deter looters.
In the central England city of Nottingham, police said rioters hurled firebombs though the window of a police station and set fire to a school and a vehicle. Some 90 people were arrested.
In the northern city of Liverpool, about 200 youths hurled missiles at police and firefighters in a second night of unrest, and 44 arrests were reported.
There also were minor clashes in the central and western England locations of Leicester, Wolverhampton, West Bromwich, Bristol and Gloucester.
In London, hundreds of stores, offices, pubs and restaurants had closed early Tuesday amid fears of fresh rioting. Normally busy streets were eerily quiet, and the smell of plywood filled the air as business owners rushed to secure their shops before nightfall.
In East London's Bethnal Green district, convenience store owner Adnan Butt, 28, said the situation was still tense.
"People are all at home — they're scared," he said.
Material from The Associated Press was used in this report