The English Defence League (EDL) gathered in Eltham, south-east London, on Tuesday evening with around 200 residents from the area.
As the number of people swelled, the mood became increasingly violent as suspected looters were chased and set upon.
In one incident, a mob attacked a bus passing through the high street after black youths, seated on the upper deck, gestured through the window. Police were quick to respond, using dog-handlers to separate the two groups.
Jack England, EDL's south-east regional organiser, claimed that the people on the streets were "patriots" and not vigilantes.