  We present spatially and spectrally resolved Br-gamma emission around the
planet-hosting, transitional Herbig Ae/Be star HD 100546. Aiming to gain
insight into the physical origin of the line in possible relation to accretion
processes, we carried out Br-gamma spectro-interferometry using AMBER/VLTI from
three different baselines achieving spatial and spectral resolutions of 2-4 mas
and 12000. The Br-gamma visibility is larger than that of the continuum for all
baselines. Differential phases reveal a shift between the photocentre of the
Br-gamma line -displaced 0.6 mas (0.06 au at 100 pc) NE from the star- and that
of the K-band continuum emission -displaced 0.3 mas NE from the star. The
photocentres of the redshifted and blueshifted components of the Br-gamma line
are located NW and SE from the photocentre of the peak line emission,
respectively. Moreover, the photocentre of the fastest velocity bins within the
spectral line tends to be closer to that of the peak emission than the
photocentre of the slowest velocity bins. Our results are consistent with a
Br-gamma emitting region inside the dust inner rim (<0.25 au) and extending
very close to the central star, with a Keplerian, disc-like structure rotating
counter-clockwise, and most probably flared (25 deg). Even though the main
contribution to the Br-gamma line does not come from gas magnetically
channelled on to the star, accretion on to HD 100546 could be magnetospheric,
implying a mass accretion rate of a few 10^-7 Msun/yr. This value indicates
that the observed gas has to be replenished on time-scales of a few months to
years, perhaps by planet-induced flows from the outer to the inner disc as has
been reported for similar systems.
