MOSCOW—Belarus President Alexander Lukashenko was sworn in for a sixth phrase in a shock inauguration ceremony, catching his opponents off guard and depriving them of an possibility to stage another mass protest from the managing of past month’s election.

Quite a few hundred men and women have been invited to Wednesday’s ceremony in the funds, Minsk, which includes senior officials, members of parliament, experts and sports and cultural figures, condition media documented. The party came six months just after the Aug. 9 vote, in which the Belarusian…