Authorities have acknowledged there were issues but dismissed allegations the vote was stolen. The fractious standoff echoes previous electoral disputes that fuelled unrest in Congo.
Tshisekedi took the oath of office in a stadium in the capital Kinshasa that was packed with supporters waving small flags, government officials, African heads of state and other foreign envoys including from the United States, China, and France.
With armed military police deployed throughout the capital, there was no immediate sign opposition supporters in Kinshasa were heeding a call from two of Tshisekedi's main opponents to protest against his re-election.
(Writing by Alessandra PrenticeEditing by Peter Graff)
By Ange Kasongo
