The invention relates to novel derivatives of 1-(2-fluorocyclopropyl)-quinolonecarboxylic acid and 1-(2-fluorocyclopropyl)-naphthyridonecarboxylic acid which are substituted in the 7 position by a 2,3,4,5,6,7-hexahydro-1H-pyrrolo[3,4-c]pyridin-2-yl or 1,2,3,4,5,6-hexahydropyrrolo[3,4-c]pyrrol-2-yl residue, to their salts, to a process for their preparation and to antibacterial agents containing these derivatives.