MOSCOW—Tens of hundreds of men and women gathered in the Belarusian capital of Minsk to protest the re-election of President Alexander Lukashenko and the intense crackdown that adopted the disputed presidential vote as the country’s protection ministry warned that disorder in the metropolis would not be tolerated.

Sunday’s demonstration, dubbed “March for a New Belarus” marked the 15th consecutive working day that Belarusians have rallied in the hopes of forcing a new election following the Aug. 9 poll in which Mr. Lukashenko claimed an 80{312eb768b2a7ccb699e02fa64aff7eccd2b9f51f6a579147b7ed58dbcded82a2} victory…