While the number of stars in the Galactic bulge with detailed chemical abundance measurements is increasing rapidly, the inner Galactic bulge (vertical bar b vertical bar < 2 degrees) remains poorly studied, due to heavy interstellar absorption and photometric crowding. We have carried out a high-resolution IR spectroscopic study of 72 M giants in the inner bulge using the CRIRES (ESO/VLT) facility. Our spectra cover the wavelength range of 2.0818-2.1444 mu m with the resolution of R similar to 50 000 and have signal-to-noise ratio of 50: 100. Our stars are located along the bulge minor axis at l = 0 degrees, b= +/- 0 degrees, +/- 1 degrees, +/- 2 degrees, and + 3 degrees. Our sample was analysed in a homogeneous way using the most current K-band line list. We clearly detect a bimodal metallicity distribution function with a metal-rich peak at similar to + 0.3 dex and a metal-poor peak at similar to -0.5 dex and no stars with [Fe/H] > + 0.6 dex. The Galactic Centre field reveals in contrast a mainly metal-rich population with a mean metallicity of + 0.3 dex. We derived [Mg/Fe] and [Si/Fe] abundances that are consistent with trends from the outer bulge. We confirm for the supersolar metallicity stars the decreasing trend in [Mg/Fe] and [Si/Fe] as expected from chemical evolution models. With the caveat of a relatively small sample, we do not find significant differences in the chemical abundances between the Northern and the Southern fields; hence, the evidence is consistent with symmetry in chemistry between North and South.