A report released by a global union federation Wednesday demanded better conditions for laborers working on the construction of Tokyo Games facilities after several "alarming" cases of suspected labor violations were uncovered.

The report from Building and Wood Workers' International (BWI), titled "The Dark Side of the Tokyo 2020 Summer Olympics," is based on interviews with construction workers and documents how low pay, overwork and poor access to grievance mechanisms are creating a "culture of fear" among crews working on Olympic projects.

BWI, headquartered in Geneva, is seeking an end to "dangerous patterns of overwork," citing the example of construction workers at the National Stadium and Olympic Village who reported being required to work up to 26 and 28 consecutive days, respectively.