Recently we developed ultrasound-modulated optical microscopy (UOM) based on a long-cavity confocal Fabry-Perot interferometer (CFPI). This interferometer is used for real-time detection of multiply scattered light modulated by high frequency (30 to 75 MHz) ultrasound pulses propagating in an optically, strongly scattering medium. In this work, we use this microscope to study the dependence of ultrasound-modulated optical signals on the optical absorption and scattering properties of objects embedded about 3 mm deep in tissue mimicking phantoms. These results demonstrate that UOM has the potential to map both optical absorption and scattering contrast. Most importantly, for the first time in the field of ultrasound-modulated optical imaging, we image blood vasculature in highly scattering tissue samples from a mouse and a rat. Therefore, UOM could be a promising tool to study the morphology of blood vasculature and blood-associated functional parameters, such as oxygen saturation.