Cameron described the scenes of burning buildings and smashed windows in London and several other British cities as "sickening," but refrained from more extreme measures such as calling in the military to help beleaguered police restore order.

Instead, he said 16,000 officers would be on the streets of the capital Tuesday night — almost tripling the number on the streets Monday night.

"People should be in no doubt that we will do everything necessary to restore order to Britain’s streets and to make them safe for the law-abiding," Cameron told reporters after a crisis meeting at his Downing Street office.

A wave of violence and looting raged across London, as authorities struggled to contain the country’s worst unrest since race riots set the capital ablaze in the 1980s. 

Parliament will return to duty on Thursday, as the political fallout from the rampage takes hold. The crisis is a major test for Cameron’s Conservative-led coalition government, which includes Liberal Democrats who had long suspected its program of harsh budget restraints could provoke popular dissent.

Cameron cut short his summer vacation in Italy, rushing home for the crisis meeting Tuesday.

In London, groups of young people rampaged for a third straight night, setting buildings, vehicles and garbage dumps alight, looting stores and pelting police officers with bottles and fireworks into early Tuesday. The spreading disorder was an unwelcome warning of the possibility of violence during London’s 2012 Summer Olympics, less than a year away.

England’s soccer match Wednesday against the Netherlands in London’s Wembley stadium was canceled to freeing up police officers for riot duty.

Police on Monday called in hundreds of reinforcements and volunteer police officers— and deployed armored vehicles in some of the worst-hit districts — but still struggled to keep pace with the chaos unfolding at flashpoints across London, in the central city of Birmingham, the western city of Bristol and the northwestern city of Liverpool.

"The violence we have seen is simply inexcusable. Ordinary people have had their lives turned upside down by this mindless thuggery," police commander Christine Jones said.

London’s police said 14 people were injured, including a man in his 60s with life-threatening injuries.

The rioters appeared to have little unifying cause — though some claimed to oppose sharp government spending cuts, which will slash welfare payments and cut tens of thousands of public sector jobs through 2015.

But many were attracted simply by the opportunity for violence. "Come join the fun!" shouted one youth in the east London suburb of Hackney, where shops were attacked and cars torched.

Rioters were left virtually unchallenged in several neighborhoods and able to plunder from stores at will or attempt to invade homes. Restaurants and stores fearful of looting closed early across London.

Simon Dance, a 27-year-old marketing manager who lives in Camden in north London, called the riots outside his apartment "very frightening."

"We locked all the doors, and my wife even packed a bag to flee. We had Twitter rolling until midnight just to keep up with the news. We were too afraid to even look out the window," he said Tuesday morning as he took pictures of a smashed Evans Cycles store and a looted Sainsbury’s grocery store.

Disorder flared throughout the night, from gritty suburbs along the capital’s fringes to central London’s posh Notting Hill neighborhood.

Police said all London police holding cells were full and prisoners were being taken to surrounding communities. 

Police were also monitoring Twitter, and warned that those who posted messages inciting the violence could face arrest.

Three people were arrested on suspicion of attempted murder after a police officer was struck by a car in north London early Tuesday. About 35 police officers have been injured in the violence.

Violence first broke out late Saturday in the low-income, multiethnic district of Tottenham in north London, where outraged protesters demonstrated against the fatal police shooting of Mark Duggan, a 29-year-old father of four who was gunned down in disputed circumstances Thursday.

A brief inquest hearing into Duggan’s death will take place Tuesday, though it will likely be several months before a full hearing.

Duggan’s death stirred old animosities and racial tensions similar to those that prompted massive riots in the 1980s, despite efforts by London police to build better relations with the city’s ethnic communities.

But, as the unrest spread, some pointed to rising social tensions in Britain as the government slashes $130 billion from public spending by 2015 to reduce the huge deficit, swollen after the country spent billions bailing out its foundering banks.

A massive blaze ravaged a 100-year-old family run furniture store in Croydon and sent thick plumes of smoke into the air, forcing nearby homes to be evacuated. In the Clapham Junction area of south London, a mob stole masks from a party store to disguise their identities and then set the building on fire.

Sony Corp. said a major blaze had broken out at its distribution center near Enfield, north London, damaging DVDs and other products. So many fires were being fought in the capital that Thames Water warned that some customers could face water pressure drops.

Dozens of people attacked shops in Birmingham’s main retail district, and clashed with police in Liverpool and Bristol.

In London’s Hackney neighborhood, hundreds of youths left a trail of burning trash and shattered glass. Looters ransacked a convenience store, filling plastic shopping bags with alcohol, cigarettes, candy and toilet paper.

East London’s diversity was on display amid the charred hulks of cars and the smell of burning plastic. Some looters were young women with manicured nails and customized BlackBerry smart phones. Others wore dreadlocks and stained shirts or appeared to be homeless.

"This is the uprising of the working class. We’re redistributing the wealth," said Bryn Phillips, a 28-year-old self-described anarchist, as young people emerged from the store with chocolate bars and ice cream cones.

Phillips claimed rioters were motivated by distrust of the police, and drew a link between the rage on London’s street and insurgent right-wing politics in the United States. "In America you have the tea party, in England you’ve got this," he said.

Some residents called for police to deploy water cannons to disperse rioters, or call on the military for support. They questioned the strength of leadership within London’s police department — particularly after a wave of resignations prompted by the country’s phone-hacking scandal.

Youths used text messages, instant messaging on BlackBerry phones and social media platforms such as Twitter to coordinate attacks and stay ahead of the police.

About 100 young people clashed with police in the Camden and Chalk Farm areas of north London. In the Peckham district of south London, where a building was set ablaze along with a bus — which was not carrying passengers — onlookers said the scene resembled a conflict zone. Cars were torched in nearby Lewisham, and in west London’s Ealing suburb the windows of each store along entire streets had been smashed.

"There’s been tension for a long time. The kids aren’t happy. They hate the police," said Matthew Yeoland, a 43-year-old teacher watching the unrest in Peckham. "It’s like a war zone and the police weren’t doing anything."

Police said Duggan was shot dead last week when police from Operation Trident — the unit that investigates gun crime in the black community — stopped a cab he was riding in.

The Independent Police Complaints Commission, which is investigating the shooting, said a "non-police firearm" was recovered at the scene. But the Guardian newspaper reported that a bullet in the officer’s radio was police-issue, indicating Duggan may not have fired at the officer.

Duggan’s partner, Semone Wilson, insisted Monday that her fiance was not connected to gang violence and urged police to offer more information about his death. But she rejected suggestions that the riots were linked to protests over his death.

"It got out of hand. It’s not connected to this anymore. This is out of control," she said.

The past year has seen mass protests against the tripling of student tuition fees and cuts to public sector pensions. In November, December and March, small groups broke away from large marches in London to loot. In the most notorious episode, rioters attacked a Rolls-Royce carrying Prince Charles and his wife Camilla to a charity concert.

However, the full impact of spending cuts has yet to be felt and the unemployment rate is stable — although it remains highest among youth, especially in areas like Tottenham, Hackney and Croydon.

Some residents insisted that joblessness was not to blame. "It’s just an excuse for the young ones to come and rob shops," said Brixton resident Marilyn Moseley, 49.

Police in Birmingham, 120 miles north of London, said 35 people had been arrested amid widespread vandalism. In Bristol, police urged residents to avoid the city center after 150 rioters went on the rampage.

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David Stringer, Raphael Satter, Sheila Norman-Culp, Meera Selva and Stephen Wilson contributed to this report.