For the past month, Iraqi troops backed by US forces have stormed through Baghdad's predominantly Sunni Arab neighbourhoods, arresting thousands in a series of sweeps aimed at deterring bomb attacks that have killed hundreds in the capital.

But while Iraqi military officers say that Operation Lightning is a necessary, if draconian, step aimed at sifting out insurgents from a civilian population that often protects them, many of those arrested claim that the campaign is a form of collective punishment against the Sunni community.