British prime minister David Cameron and other senior politicians were planning to fly back from holiday on Monday as riots spread through London with potent images of the capital ablaze beamed around the world and emboldened youths attacking in broad daylight.

Both Theresa May, home secretary, and Boris Johnson, London mayor returned to the UK to lead the political response to the violence, which started in Tottenham after a peaceful vigil for a local resident shot dead during a police operation.

In a sign that rioters were growing in confidence, between 50 and 100 youths gathered on a busy junction in Hackney, east London, during the early afternoon, throwing missiles at police and setting light to cars. Local shops pulled down their shutters and the shopping centre closed as owners feared a repeat of the looting suffered by retailers in Tottenham, Walthamstow and Brixton over the weekend.