A method for the solution of the inverse problem of radiative transfer is presented which utilizes the internal fluxes measured at different depths and in different directions with optical radiance microprobes in dense multiple scattering media. The method yields optical cross-sections and the phase function for the sample even when these parameters are depth dependent. The sensitivity analysis shows that the theoretical errors caused by the finite number of measurements as well as by the non-uniform directional sensitivity of the microprobes can be held on a low level; even the fourth Legendre coefficient of the unknown phase function can be recovered to the accuracy of 10%.