1. A medical image processing apparatus, comprising: a storage that stores three-dimensional images of a tubular body; a virtual endoscopic image generator, implemented by circuitry, that generates, by using the three-dimensional images of the tubular body, virtual endoscopic images of an inside of a tract of the tubular body according to a view point location and a view direction inside the tract of the tubular body, the virtual endoscopic images including a virtual endoscopic image of an observation region; a region identifier, implemented by the circuitry, that determines the observation region, the observation region including a volume from the view point location along a line-of-sight of the view direction to the tract of the tubular body ; and an image generator, implemented by the circuitry, that generates a cross-sectional image of the tubular body indicating the observation region, the cross-sectional image being distinguishably displayed on a virtual endoscopic image of the virtual endoscopic images obtained from the three-dimensional images, wherein an area representing the observation region is superimposed on the cross-sectional image, and the area is filled to distinguish the observation region in the tubular body.