French presidential candidates on Wednesday seized on a night of rioting between police and youths at the Gare du Nord train station in Paris to relaunch the debate about law and order less than four weeks before the presidential election.

Shop windows were smashed, ticket machines turned over and fires were started in waste bins, as several hundred youths, many of immigrant origin, fought running battles on Tuesday night with riot police who used tear gas to restore calm to the mainline station.