(CNN) Tensions continue to rise on the streets of the Bolivian administrative capital La Paz, with angry crowds accusing authorities of fraud in Sunday's presidential election.

Protesters and the opposition claim electoral authorities manipulated the vote count in favor of President Evo Morales, the nation's longtime socialist leader. Protests have turned violent over the result, with demonstrators burning ballot boxes and clashing with riot police in several cities.

Preliminary results released hours after polls closed Sunday showed a tight margin between Morales and former leader Carlos Mesa, which would have prompted a runoff vote in December. To avoid another round of voting, a candidate needs a 10-point advantage.

But opposition groups and international observers grew suspicious after election officials stopped the count for 24 hours Sunday without any explanation. When counting resumed, Morales's lead had jumped, making him certain to be an outright winner.

Bolivian opposition protestors set on fire the electoral offices in Sucre on October 21, 2019.

According to the most recent report of the Supreme Electoral Court, Morales had a lead of 46.4% of the votes and Mesa 37.07%, with 95.63% of verified votes counted, which means that so far there is a possibility of a second presidential round.

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