Britain's worst riots in decades raged into Wednesday, August 10, as youths ran amok in Manchester and the Midlands but London was quiet with 16,000 police swamping the streets to stem violence, AFP reported.

In Manchester, youths smashed shop windows and looted shops and chased photographers away from the scene in what police described as the city's worst violence in 30 years.

Elsewhere, hooded rioters set fire to buildings in West Bromwich and Wolverhampton and a police station in nearby Nottingham was firebombed, although there were no reported injuries. Looters also targeted shops in Birmingham for another night and 200 rioters pelted police with missiles in Liverpool as the nation faced up to a fourth day of unrest.

But in London there was no repeat of the wave of violence which left parts of the capital in flames on Monday night, as vigilante mobs took to the streets to defend their communities.

Police were bracing for more trouble after what they said was the worst night of disorder in living memory in the capital, and their numbers were ramped up from 6,000 to 16,000 on Tuesday night as Prime Minister David Cameron vowed to do "everything necessary to restore order to the streets".

Shops in many parts of London closed early and put down their shutters on the advice of the police.

Scotland Yard said early Wednesday that 768 people had been arrested in London for violence, disorder and looting.