The invention relates to antibacterial compounds of formula I wherein R1 is H or halogen; R2 is alkynyloxy or the group M; R3 is H or halogen; M is one of the groups wherein A is a bond, CH2CH2, CH═CH or C≡C and R1A, R2A, R3A, R1B and R1C are as defined in claim 1; and salts thereof.