PARIS — The Muslim member of Bosnia’s tripartite presidency on Thursday asked the highest United Nations court to reopen a 2007 case that cleared Serbia of genocide during the war in Bosnia.

The request by the Muslim member, Bakir Izetbegovic, is likely to fan the simmering political tension in a region still torn by the war that broke up Yugoslavia in the 1990s.

Nationalists and pro-Serb secessionists in Bosnia, who have received support from both Serbia and Russia, could be emboldened by the move, critics said.

Moscow has been courting Serbia and Bosnian Serbs, while also covertly intervening in neighboring Macedonia and Montenegro, as it tries to regain its historical influence in the Balkans.