Prime Minister David Cameron recalled parliament and ordered thousands of extra police onto the streets after Britain's worst rioting in decades left parts of London and other cities in flames.
After cutting short his holiday in Italy to return for an emergency meeting on the riots, Cameron said his government would "do everything necessary to restore order to the streets, and to make them safe" for law-abiding people.
Addressing the mainly young men responsible for the "sickening scenes" of looting and arson, he said: "You will feel the full force of the law. And if you are old enough to commit these crimes, you are old enough to face the punishments."
Riots swept through London and in other cities overnight Monday, the third consecutive night of violence which began in the north London district of Tottenham on Saturday following the shooting of a local man by police.
The unrest is the worst since the 1980s and has raised questions about security in London ahead of the Olympic Games which take place in the east of the capital in a year's time.
Newspapers carried dramatic pictures of burning shops amid headlines such as "Rule of the Mob" (Daily Telegraph) and "Mob Rule as Police Surrender Streets" (The Times).
In some areas, rioters took control of the streets with little sign of a police presence -- in Clapham, a predominantly affluent area of southwest London, hundreds looted a department store for at least two hours, witnesses said.
Cameron said that all police leave had been cancelled and there would be 16,000 officers on the streets of London on Tuesday night, compared to the 6,000 deployed on Monday evening.
More than 450 people have been arrested in London in the last three days, too many to hold in the city's police station jails.
Despite the scenes of devastation, Acting Police Commissioner Tim Godwin said there were "no plans" for the army to get involved.
The speaker of the House of Commons has agreed to recall parliament on Thursday so lawmakers could debate their response to the riots, Cameron said -- a highly unusual move highlighting the seriousness of the crisis.
In a sign of the fallout from the riots, the Football Association cancelled Wednesday's friendly between England and the Netherlands at Wembley Stadium in north London because of the violence.
It began on Saturday night in the ethnically-mixed north London district of Tottenham, following a protest against the death of a local man, Mark Duggan, in a police shooting two days earlier.
An inquest into the 29-year-old's death opened on Tuesday, and heard that he died of a single gunshot wound to the chest.
Duggan, a father of four, was shot after the taxi he was travelling was stopped by police during an operation against gun crime in the black community.
Copycat riots broke out in other flashpoints areas on Sunday, and by Monday night they had spread across the city, from the wealthy districts of Notting Hill and Clapham, inner-city Peckham and Hackney, and suburban Croydon and Ealing.
The violence was often directed at police officers, including in Brent, where three people were arrested for attempted murder after an officer was hit by a car. He was hospitalised, but was in a stable condition.
Some 44 police officers were injured overnight Monday, in addition to at least 35 who were hurt on the previous two evenings, police said.
The violence also spread outside London on Monday night, including to Liverpool, where hundreds of rioters rampaged through the streets of the northwest city for several hours, setting cars and dustbins alight.
Police in Birmingham said they had made 100 arrests as youths ran riot and looted shops in the city centre overnight, while police in the western city of Bristol battled to contain a mob of 150 youths.
Some of the worst destruction was in Croydon where an entire block of buildings -- including a 100-year-old family furniture business -- was burned down, sending flames leaping into the night sky.
The owner of the furniture business, Trevor Reeves, told Sky News: "Words fail me. It's just gone, it's five generations. My father is distraught at the moment. It's just mindless thuggery."