  We report the results of time-resolved photometric and spectroscopic
near-infrared observations of the Ofpe/WN9 star and LBV candidate GCIRS34W in
the Galactic Centre star cluster. Diffraction limited resolution photometric
observations obtained in H and K bands show a strong, non-periodic variability
on time scales from months to years in both bands accompanied by variations of
the stellar colour. Three K band spectra obtained in 1996, 2003 and 2004 with
integral field spectrometers are identical within their accuracies and exclude
significant spectroscopic variability. The most probable explanation of the
stellar photometric variability is obscuration by circumstellar material
ejected by the star. The approximated position of GCIRS34W in a HR diagram is
located between O supergiants and LBVs, suggesting that this star is a
transitional object between these two phases of stellar evolution.
