Magnetic susceptibility χ of Bi2-x Mn x Se3 (x = 0.01-0.2) was measured in the temperature range 4.2-300 K. For all the samples, a Curie-Weiss behaviour of χ(T) was revealed with effective magnetic moments of Mn ions corresponding to the spin value S = 5/2, which couple antiferromagnetically with the paramagnetic Curie temperature Θ ~ -50 K. In addition, for the samples of nominal composition x = 0.1 and 0.2 the effect of a hydrostatic pressure P up to 2 kbar on χ has been measured at fixed temperatures 78 and 300 K that allowed to estimate the pressure derivative of Θ to be dΘ/dP ~ -0.8 K kbar(-1). Based on the observed behaviour of Θ with varied Mn concentration and pressure, a possible mechanism of interaction between localized Mn moments is discussed.