MOSCOW—Belarus opposition leader Svetlana Tikhanovskaya re-emerged following fleeing to neighboring Lithuania, calling for new protests and piling further more strain on the country’s longtime leader, President Alexander Lukashenko, following past weekend’s disputed election.

Ms. Tikhanovskaya, a political newcomer who stepped forward as a candidate following her husband was detained in Could, urged protesters to demand an official investigation into the election and claimed she experienced files suggesting she experienced received up to 70{312eb768b2a7ccb699e02fa64aff7eccd2b9f51f6a579147b7ed58dbcded82a2} of the vote