A device for injecting air into an exhaust system fitted with catalytic cleaner for a supercharged Otto engine, in whose intake manifold is incorporated an air compressor driven by the engine, which compressor causes the supercharging. An air bleeding duct is arranged for adjustable bleeding of air from the intake manifold and to supply this air as additional air to the catalytic cleaner. This air bleeding duct extends from a point in the intake manifold downstream from the compressor to a point in the exhaust system upstream from the catalytic cleaner. In an inlet section of the intake manifold, located upstream from the compressor, there is an electronically controlled device for idle control of the engine as the air is bled via the air bleeding duct. An extra throttle valve is incorporated in the intake manifold immediately downstream from the bleeding point for maintaining a minimum excess pressure immediately after the compressor in the case of a rich fuel/air mixture and/or before the engine is operating at lambda=1.