  A new type of high-energy binary systems has been revealed by the INTEGRAL
satellite. These sources are in the course of being unveiled by means of
multi-wavelength optical, near- and mid-infrared observations. Among these
sources, two distinct classes are appearing: the first one is constituted of
intrinsically obscured high-energy sources, of which IGR J16318-4848 seems to
be the most extreme example. The second one is populated by the so-called
supergiant fast X-ray transients, with IGR J17544-2619 being the archetype. We
report here on multi-wavelength optical to mid-infrared observations of these
systems. We show that in the case of the obscured sources our observations
suggest the presence of absorbing material (dust and/or cold gas) enshrouding
the whole binary system. We then discuss the nature of these two different
types of systems.
