Left panel: X-ray to TeV energies spectrum of the Galactic centre. The data are adopted from Baganoff et al. (2003) (green solid cross, X-ray quiescent), Porquet et al. (2008) (green dashed cross, X-ray flaring), this work (red points) and Aharonian et al. (2009) (blue points, HESS). The INTEGRAL/PICsIT upper limits (this work) are shown in black. The leptonic model proposed in this work for the low-density case is shown with the solid black line. Right panel: hadronic model of γ-ray radiation from the broken power-law distribution of protons. The model significantly under predicts the flux at ≲150 MeV energies (black line); see text for details. The statistical error is shown with thick errorbars, while the thin ones indicate systematic levels, which are shown in the left panel.