A leading opposition activist and several other members of an opposition council in Belarus went missing Monday and their colleagues feared they were detained as part of the authorities’ efforts to squelch nearly a month of protests against the re-election of the country’s authoritarian leader. Maria Kolesnikova, a member of the Coordination Council created by the opposition to facilitate talks with President Alexander Lukashenko on a transition of power, was reportedly put on a minibus in the capital, Minsk, and driven away by unidentified people.