London: The British capital continued to smoulder under a series of "copycat" riots that engulfed the city for a second day, with looting and arson reported in new areas, just miles from the site of next year's Olympic Games, prompting authorities to arrest as many as 160 people.

Groups of masked youth looted shops, attacked police officers and set fire to vehicles in raging violence, sparked by the killing of a youth in police shooting in Tottenham, raising questions over security of the 2012 Games.

London police launched a massive investigation into what they described as "copycat criminal" violence, as Home Secretary Theresa May rushed back from her summer holiday.

She warned that those responsible "will be made to face the consequences of their actions".

Irate mobs looted a giant electrical retail store in the black-dominated southern area of Brixton as violence was reported in several boroughs in north, south and east London
following earlier trouble in Tottenham in the north.

Even the posh Oxford Circus at the heart of the city's tourist area also reported sporadic violence.

May, who is flying back today from her summer holiday has been in contact with senior politicians and police officials after the fatal shooting of Mark Duggan, 29, by police during a peaceful protest in Tottenham on Thursday prompted violent riots on Saturday night.

May warned that those responsible "will be made to face the consequences of their actions" and called on all members of local communities to work constructively with the police to help them bring "these criminals to justice". The looting across London was carried out by "small and mobile groups", the Scotland Yard said.

Deputy Assistant Commissioner Steve Kavanag admitted on Radio 4 that there were too few officers in Tottenham on Saturday night. But he blamed Twitter for fueling looting and violence.

"Social media and other methods have been used to organize these level of greed and criminality," he added.

Scotland Yard said nine officers were injured, including three who were hospitalised after being hit by a fast moving vehicle.

Police said 16 people have been charged with offences including burglary, theft and violent disorder.

Meanwhile, the bullet fired at a police officer before Duggan was shot dead by armed police team is understood to be a police-issue round, media reports said citing initial
forensic tests.

It was initially suggested that Duggan died after an exchange of fire with police officers. A bullet was found lodged in an officer's radio.

The Independent Police Complaints Commission (IPCC) has launched an inquiry into the shooting.

A spokesman for the IPCC said, "We await further forensic analysis to enable us to have a fuller and more comprehensive account of what shots were discharged".