London police launched a "major investigation" into the city's worst rioting in years as violence sparked by the death of a local man in a police shooting raged on early Monday.
Thousands looted a giant electrical retail store in the southern area of Brixton in Monday's early hours and gangs of youths pelted police with missiles, AFP correspondents reported.
Scotland Yard said "copycat" looting had spread to a number of boroughs in the capital's north, east and south, while a mob of around 50 youths damaged property in Oxford Circus, at the heart of the city's tourist area.
Several arrests were made after youths vandalised a police car and smashed windows in Enfield, a north London suburb three miles from Tottenham, the area at the heart of the previous night's mayhem.
Additional police resources were deployed in the volatile neighbourhoods with three officers requiring hospital treatment after being hit by a car.
Commander Christine Jones said: "This is a challenging situation with small pockets of violence, looting and disorder breaking out on a number of boroughs."
In the first night of violence, homes were torched, two police cars and a double-decker bus torched and shops looted late Saturday in Tottenham, conjuring memories of 1985 riots in the same area and dampening the mood in a city hosting the Olympic Games in a year.
Police said 26 of its officers were hurt, while three members of the public also needed treatment following the surprise violence. By Sunday, all the injured police officers had been discharged from hospital.
A total 55 arrests were made after Saturday's riots. Prime Minister David Cameron's office described the violence as "utterly unacceptable."
Metropolitan police announced that officers working on the Operation Withern probe would interview witnesses and review hours of CCTV footage to locate the Tottenham rioters.
The violence followed a protest over the death of a 29-year-old man last Thursday during an apparent exchange of gunfire with police.
The killing of Mark Duggan, a father-of-four, was "absolutely regrettable," police commander Adrian Hanstock said in a statement, adding that an investigation into the shooting was underway.
According to the Guardian newspaper, initial ballistics tests on a bullet which was found lodged in a police officer's radio when Duggan was shot revealed it was a police issue bullet, raising doubts over the early explanation of events.
Duggan's brother Shaun Hall called for peace.
"I know people are frustrated, they're angry out there at the moment, but I would say please try and hold it down. Please don't make this about my brother's life, he was a good man," he told Sky News television.
Staff at the looted Curry's electrical store in Tottenham told AFP that the thieves had immediately headed to the security rooms and deactivated the cameras, suggesting professional gangs had flocked to the area.
London has seen student and trade union protests turn ugly in the last 12 months but this outbreak of rioting was the worst seen for years away from the capital's centre.
One witness said Saturday's scene resembled the Blitz, or when parts of London burned following German bombing in World War II.
Scene: London riot turns district into war zone
"So many people have lost everything. It's just crazy. It looks like it's the Second World War. It looks like the Blitz where we were living," Tottenham resident Stuart Radose told Sky News television.
Duggan was killed when specialist firearms officers stopped a minicab in which he was travelling to carry out a pre-planned arrest.
The Independent Police Complaints Commission, which investigates all police shootings, said they were accompanied by officers from Trident, the unit focused on tackling gun crime in the black community.
The march against Duggan's death began at Broadwater Farm, a 1960s public housing estate in Tottenham that is notorious across Britain.
In 1985, police constable Keith Blakelock was hacked to death on the estate in some of the worst urban rioting in Britain during the past 30 years.