British authorities might use rubber or plastic bullets to quell rioting that has swept the city for a third night and spread to other cities, a senior London police officer says.

Such bullets are "one of the tactics" being considered, Deputy Assistant Commissioner Stephen Kavanagh said Tuesday. Plastic bullets have never been used before during British disturbances.

Kavanagh's comments come as British Prime Minister David Cameron vowed Tuesday to do everything necessary to restore order and punish those responsible for the violent riots.

Cameron cut short his holidays to return to London to address the worst rioting in the country in decades, saying he will boost police presence to 16,000 officers from 6,000 by Tuesday night, and warning that the culprits "will feel the full force of the law.

"This is criminality, pure and simple," Cameron said outside 10 Downing Street, "and a strong warning to those involved in rioting that they will face full the force of the law, no matter how young they are.

"If you are old enough to commit these crimes, you are old enough to face the punishment," he added. "You are not only wrecking the lives of others and ... your communities, you are potentially wrecking your own life too."

Cameron also announced the rare move of recalling Parliament early from its summer recess, on Thursday, to deal with the riots.

"Parliament only ever gets recalled in times of grave national crisis, an indication of how bad things have got," CBC freelance correspondent Dominic Valitis reported.

450 arrested over 3 nights

Police said 450 people had been arrested over three nights of rioting that began late Saturday in London's northern Tottenham district when a peaceful protest over the police shooting of a suspect turned violent, leaving parts of the street charred and its shops looted.

All of London police holding cells were full and prisoners were being taken to surrounding communities. At least 69 people have been charged with offences.

Three people have been arrested over the alleged attempted murder of a police officer, British police said Tuesday. The suspects were detained and arrested in the Brent area of north London, after a police officer was struck by a car and hospitalized in the country's worst unrest since race riots set the capital ablaze in the 1980s.

The officer and a colleague, who suffered minor injuries, had stopped a number of cars in the belief that the occupants had been involved in the looting of a nearby electrical store.

Police say in a statement the officer was seriously hurt as one of the cars drove away from the scene. It was later stopped and the three people inside were arrested.

Some have blamed the unrest on unemployment, insensitive policing and frustration across Britain over the government's austerity budget, which will bring deep cuts to social services and welfare payments.


A 'broom brigade' gathers Tuesday at the site of rioting in Clapham to volunteer in cleanup efforts. (Alison Crawford/CBC)

Police have called in hundreds of reinforcements, and made a rare decision to deploy armoured 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.

Authorities acknowledged that major new bouts of violence had badly stretched their resources.

"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.

BlackBerry responds

Once the preserve of businesspeople, Canadian manufactured BlackBerry handsets are popular with teenagers in Britain, thanks to their free, fast instant messaging system.

It's believed small groups of youths used text messages, instant messaging on their BlackBerrys and social media platforms such as Twitter to co-ordinate their attacks in London and stay ahead of police.

The violence has prompted BlackBerry manufacturer Research in Motion, based in Waterloo, Ont., to issue a statement saying it was assisting authorities in their investigation and "feel for those impacted by the riots in London."

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

Others appeared attracted simply by the opportunity for violence.

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

Disorder flared throughout the night, from gritty suburbs along the capital's fringes to the Notting Hill neighbourhood. London's Ambulance Service said it had treated 16 patients, of whom 15 were hospitalized.

After dawn, police said, the unrest appeared to calm, either quelled by police or after rioters drifted away.

Brief inquest expected into father of 4's death

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.

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

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

Canadians warned

Canada's Foreign Affairs Department issued this notice on Tuesday advising Canadians travelling to London:

"Violent riots and looting have been taking place in London, outlying areas and beyond (including Tottenham, Hackney, Brixton, Lewisham, Peckham, Croydon and Birmingham) since August 6 and have led to clashes between rioters and police. Canadians in any affected areas should be vigilant, monitor local media for current information and follow the advice of local authorities."

"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.

About 100 young people clashed with police in the Camden and Chalk Farm areas of north London, smashing their way into a bicycle store and mobile phone shop.


A police officer stands guard as firefighters work to extinguish the flames of a blazing store in Woolwich, southeast London, on Tuesday. ((Jon Boyle/Reuters))

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.

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.

With files from CBC News, BBC