[en] An earlier studies, it was found that bulk sintered MgB_2 samples contained numerous voids which hinder the current flow. Therefore, a series of bulk MgB_2 superconductors with Ag contents of 0-10 wt% was prepared in order to improve the critical current densities and the mechanical performance. Several samples were fabricated using a solid state reaction in pure Ar atmosphere at the optimal reaction temperature of 775 C. Thorough microstructural observations obtained from scanning electron microscopy (SEM) and atomic force microscopy (AFM) indicate that metallic Ag particles are embedded in the void regions.Furthermore, nanometer-sized AgMg_3 particles are also present within the MgB_2 matrix, leading to improved flux pinning. Small samples cut from the bulks were characterized by transport measurements (R(T,B) and I/V characteristics) in magnetic fields up to 8 T and by magnetization loops measured using a SQUID magnetometer.