  We combine infrared spectra in the I, J, H and K bands together with JHK
photometry to characterize the spectral type, luminosity class and distance to
the infrared counterparts to five INTEGRAL sources. For SAX J18186-1703 and IGR
J18483-0311, we present the first intermediate-resolution spectroscopy
reported. We find that four systems harbour early-type B supergiants. All of
them are heavily obscured, with E(B-V) ranging between 3 and 5, implying visual
extinctions of ~ 9 to 15 magnitudes. We refine the published classifications of
IGR J18027-2016 and IGR J19140+0951 by constraining their luminosity class. In
the first case, we confirm the supergiant nature and rule out class III. In the
second case, we propose a slightly higher luminosity class (Ia instead of Iab)
and give an improved value of the distance based on new optical photometry.
Owing to their infrared and X-ray characteristics, IGR J18027-2016 and IGR
J19140+0951, emerge as Supergiant X-ray binaries with X-ray luminosities of the
order of Lx ~ [1-2] x 10^{36} erg/s, while SAX J1818.6-1703 and IGR
J18483-0311, turn out to be Supergiant Fast X-ray Transients at 2 and 3 kpc,
respectively. Finally, XTE J1901+014 emerges as a puzzling source: its X-ray
behaviour is strongly reminiscent of the SFXTs but a supergiant nature is
firmly ruled out for the counterpart. We discuss several alternative scenarios
to explain its behaviour.
