A compound of formula I wherein X represents N or CH; R 1 represents H or halogen; R 2 represents (C 3 -C 4)alkynyloxy or the group M; R 3 represents H or halogen; M is one of the groups M A and M B represented below wherein A represents a bond, CH 2 CH 2, CH=CH or C=C; R 1A represents H or halogen; R 2A represents H, (C 1 -C 3)alkoxy or halogen; R 3A represents H, (C 1 -C 3)alkoxy, hydroxy(C 1 -C 4)alkoxy, (C 1 -C 3)alkoxy(C 2 -C 3)alkoxy, (C 1 -C 3)thioalkoxy, trifluoromethoxy, amino, hydroxy(C 1 -C 4)alkyl, 2-hydroxyacetamido, 1-aminocyclopropyl, 1-hydroxymethyl-cycloprop-1-yl, 1-((phosphonooxy)methyl)cyclopropyl, 1-(((dimethylglycyl)oxy)methyl)cyclopropyl, trans -2-hydroxymethyl-cycloprop-1-yl, 1,2-dihydroxyethyl, 3-hydroxyoxetan-3-yl, 3-(hydroxy(C 1 -C 3)alkyl)oxetan-3-yl, 3-aminooxetan-3-yl, 3-hydroxythietan-3-yl, morpholin-4-yl(C 2 -C 3)alkoxy, morpholin-4-yl-(C 1 -C 2)alkyl, oxazol-2-yl or [1,2,3]triazol-2-yl; and R 1B represents hydroxy(C 1 -C 3)alkyl, dihydroxy(C 1 -C 4)alkyl, amino(C 1 -C 3)alkyl, (dimethylamino)methyl, 1-hydroxymethyl-cycloprop-1-yl, trans -2-(1,2-dihydroxyethyl)cycloprop-1-yl, 1-methyl-2-hydroxymethyl-cycloprop-1-yl, 2-(hydroxymethyl)-2-methylcyclopropyl, 1-aminomethyl-cycloprop-1-yl, trans -2-hydroxymethyl-cycloprop-1-yl, 1-fluoro-2-(hydroxymethyl)cyclopropyl, 2-fluoro-2-(hydroxymethyl)cyclopropyl, 1-(hydroxymethyl)cyclobutyl, 3-hydroxyoxetan-3-yl, 3-hydroxymethyl-oxetan-3-yl, 3-hydroxythietan-3-yl, 1-(2-hydroxyacetyl)azetidin-3-yl, 1-(2-aminoacetyl)azetidin-3-yl, 1-glycylazetidin-3-yl, 1-(2-amino-2-methylpropanoyl)azetidin-3-yl, 3-(2-aminoacetamido)cyclopentyl, trans -( cis -3,4-dihydroxy)-cyclopent-1-yl, 3-hydroxymethylbicyclo[1,1,1]pentan-1-yl, 3-hydroxymethylbicyclo[1,1,1]pentan-1-yl, piperidin-4-yl, 1-(2-hydroxyacetyl)piperidin-4-yl, 4-hydroxytetrahydro-2 H -pyran-4-yl, 5-aminotetrahydro-2 H- pyran-2-yl, ( 1s, 3r)-(1-hydroxy-3-(hydroxymethyl)cyclobutyl)methyl or 3-hydroxyoxetan-3-ylmethyl; or a salt of this compound. X represents N or CH; R 1 represents H or halogen; R 2 represents (C 3 -C 4)alkynyloxy or the group M; R 3 represents H or halogen; M is one of the groups M A and M B represented below wherein A represents a bond, CH 2 CH 2, CH=CH or C=C; R 1A represents H or halogen; R 2A represents H, (C 1 -C 3)alkoxy or halogen; R 3A represents H, (C 1 -C 3)alkoxy, hydroxy(C 1 -C 4)alkoxy, (C 1 -C 3)alkoxy(C 2 -C 3)alkoxy, (C 1 -C 3)thioalkoxy, trifluoromethoxy, amino, hydroxy(C 1 -C 4)alkyl, 2-hydroxyacetamido, 1-aminocyclopropyl, 1-hydroxymethyl-cycloprop-1-yl, 1-((phosphonooxy)methyl)cyclopropyl, 1-(((dimethylglycyl)oxy)methyl)cyclopropyl, trans -2-hydroxymethyl-cycloprop-1-yl, 1,2-dihydroxyethyl, 3-hydroxyoxetan-3-yl, 3-(hydroxy(C 1 -C 3)alkyl)oxetan-3-yl, 3-aminooxetan-3-yl, 3-hydroxythietan-3-yl, morpholin-4-yl(C 2 -C 3)alkoxy, morpholin-4-yl-(C 1 -C 2)alkyl, oxazol-2-yl or [1,2,3]triazol-2-yl; and R 1B represents hydroxy(C 1 -C 3)alkyl, dihydroxy(C 1 -C 4)alkyl, amino(C 1 -C 3)alkyl, (dimethylamino)methyl, 1-hydroxymethyl-cycloprop-1-yl, trans -2-(1,2-dihydroxyethyl)cycloprop-1-yl, 1-methyl-2-hydroxymethyl-cycloprop-1-yl, 2-(hydroxymethyl)-2-methylcyclopropyl, 1-aminomethyl-cycloprop-1-yl, trans -2-hydroxymethyl-cycloprop-1-yl, 1-fluoro-2-(hydroxymethyl)cyclopropyl, 2-fluoro-2-(hydroxymethyl)cyclopropyl, 1-(hydroxymethyl)cyclobutyl, 3-hydroxyoxetan-3-yl, 3-hydroxymethyl-oxetan-3-yl, 3-hydroxythietan-3-yl, 1-(2-hydroxyacetyl)azetidin-3-yl, 1-(2-aminoacetyl)azetidin-3-yl, 1-glycylazetidin-3-yl, 1-(2-amino-2-methylpropanoyl)azetidin-3-yl, 3-(2-aminoacetamido)cyclopentyl, trans -( cis -3,4-dihydroxy)-cyclopent-1-yl, 3-hydroxymethylbicyclo[1,1,1]pentan-1-yl, 3-hydroxymethylbicyclo[1,1,1]pentan-1-yl, piperidin-4-yl, 1-(2-hydroxyacetyl)piperidin-4-yl, 4-hydroxytetrahydro-2 H -pyran-4-yl, 5-aminotetrahydro-2 H- pyran-2-yl, ( 1s, 3r)-(1-hydroxy-3-(hydroxymethyl)cyclobutyl)methyl or 3-hydroxyoxetan-3-ylmethyl; or a salt of this compound. wherein A represents a bond, CH 2 CH 2, CH=CH or C=C; R 1A represents H or halogen; R 2A represents H, (C 1 -C 3)alkoxy or halogen; R 3A represents H, (C 1 -C 3)alkoxy, hydroxy(C 1 -C 4)alkoxy, (C 1 -C 3)alkoxy(C 2 -C 3)alkoxy, (C 1 -C 3)thioalkoxy, trifluoromethoxy, amino, hydroxy(C 1 -C 4)alkyl, 2-hydroxyacetamido, 1-aminocyclopropyl, 1-hydroxymethyl-cycloprop-1-yl, 1-((phosphonooxy)methyl)cyclopropyl, 1-(((dimethylglycyl)oxy)methyl)cyclopropyl, trans -2-hydroxymethyl-cycloprop-1-yl, 1,2-dihydroxyethyl, 3-hydroxyoxetan-3-yl, 3-(hydroxy(C 1 -C 3)alkyl)oxetan-3-yl, 3-aminooxetan-3-yl, 3-hydroxythietan-3-yl, morpholin-4-yl(C 2 -C 3)alkoxy, morpholin-4-yl-(C 1 -C 2)alkyl, oxazol-2-yl or [1,2,3]triazol-2-yl; and R 1B represents hydroxy(C 1 -C 3)alkyl, dihydroxy(C 1 -C 4)alkyl, amino(C 1 -C 3)alkyl, (dimethylamino)methyl, 1-hydroxymethyl-cycloprop-1-yl, trans -2-(1,2-dihydroxyethyl)cycloprop-1-yl, 1-methyl-2-hydroxymethyl-cycloprop-1-yl, 2-(hydroxymethyl)-2-methylcyclopropyl, 1-aminomethyl-cycloprop-1-yl, trans -2-hydroxymethyl-cycloprop-1-yl, 1-fluoro-2-(hydroxymethyl)cyclopropyl, 2-fluoro-2-(hydroxymethyl)cyclopropyl, 1-(hydroxymethyl)cyclobutyl, 3-hydroxyoxetan-3-yl, 3-hydroxymethyl-oxetan-3-yl, 3-hydroxythietan-3-yl, 1-(2-hydroxyacetyl)azetidin-3-yl, 1-(2-aminoacetyl)azetidin-3-yl, 1-glycylazetidin-3-yl, 1-(2-amino-2-methylpropanoyl)azetidin-3-yl, 3-(2-aminoacetamido)cyclopentyl, trans -( cis -3,4-dihydroxy)-cyclopent-1-yl, 3-hydroxymethylbicyclo[1,1,1]pentan-1-yl, 3-hydroxymethylbicyclo[1,1,1]pentan-1-yl, piperidin-4-yl, 1-(2-hydroxyacetyl)piperidin-4-yl, 4-hydroxytetrahydro-2 H -pyran-4-yl, 5-aminotetrahydro-2 H- pyran-2-yl, ( 1s, 3r)-(1-hydroxy-3-(hydroxymethyl)cyclobutyl)methyl or 3-hydroxyoxetan-3-ylmethyl; or a salt of this compound.