In this Letter we investigate the origin of the near-infrared emission of the Herbig Ae star MWC 758 on sub-astronomical unit ( AU ) scales using spectrally dispersed low resolution ( R=35 ) AMBER/VLTI interferometric observations both in the H ( 1.7 \mu m ) and K ( 2.2 \mu m ) bands .
We find that the K band visibilities and closure phases are consistent with the presence of a dusty disk inner rim located at the dust evaporation distance ( 0.4 AU ) while the bulk of the H band emission arises within 0.1 AU from the central star .
Comparing the observational results with theoretical model predictions , we suggest that the H band emission is dominated by an hot gaseous accretion disk .