People hold flags and posters during a march to commemorate Kremlin critic Boris Nemtsov, who was shot dead on Friday night, in central Moscow March 1, 2015. Opposition supporters march through Moscow on March 1 in memory of Nemtsov, whose murder has increased concern about Russia's future among opponents of President Vladimir Putin. REUTERS/Maxim Shemetov (RUSSIA - Tags: CRIME LAW POLITICS CIVIL UNREST)