Violence broke out first in Tottenham, then Enfield, Walthamstow and Brixton last night, following the fatal shooting of 29-year-old Mark Duggan last Thursday.
Rioters attacked police officers and set buildings and cars on fire, while looters caused further damage by breaking into shops.
Nims Obunge, pastor and Chief Executive of the Peace Alliance, said there were questions surrounding Duggan's death that needed to be answered.
"We need justice, that's what they're crying out for," he told the BBC.
"They are crying for justice and we can't ignore that.
"It is right that this community should have the questions that it has answered and until those questions are answered I don't think we can effectively re-build the community we want to rebuild."
Alan Argent, minister of Trinity Congregational Church in Brixton, said he was woken in the early hours of Monday morning by the sounds of looting and police moving in.
He appealed for "restraint" and asked that Christians pray for Brixton and other areas affected by the riots.
"It's a rather disturbing reminder of the unrest in the late seventies and 1980s and we just have to be hopeful that things don't escalate," he said.
"But it is a worry and we are concerned that some people may lose their jobs at a time of recession, because people may move out if they don't feel this is a safe area, shops might close down and we may lose investment in the area.
"Brixton is a place of hope and promise. It has a cosmopolitan population that gets on extraordinarily well and the riots shouldn't be allowed to set back the progress that has been made."