MOSCOW (AP) — Russia's Investigative Committee has opened a criminal case into the weekend protest in Moscow where police detained nearly 1,400 people, indicating charges could be filed that carry prison sentences of up to 15 years. No individuals were immediately named in the case that was announced Tuesday. The potential charges include calling for or participating in mass disorder. An arrest-monitoring group says Russian police detained nearly 1,400 people in the Saturday protest against election authorities for excluding opposition candidates from the Sept. 8 ballot for the Moscow city election. Police beat some demonstrators harshly with truncheons. In his first public comments on the disorder, Moscow Mayor Sergei Sobyanin said Tuesday the protesters "forced police to use force that in this situation was completely appropriate."