  We give formulas for calculating the unramified Brauer group of a homogeneous
space $X$ of a semisimple simply connected group $G$ with finite geometric
stabilizer $\bar F$ over a wide family of fields of characteristic 0. When $k$
is a number field, we use these formulas in order to study the Brauer-Manin
obstruction to the Hasse principle and weak approximation. We prove in
particular that the Brauer-Manin pairing is constant on $X(k_v)$ for every $v$
outside from an explicit finite set of non archimedean places of $k$.
