LA PAZ, Bolivia — President Evo Morales of Bolivia faced stinging accusations of election irregularities by international observers and violent protests in the streets on Monday as an updated tally of votes cast in the country’s presidential election appeared to give him a big enough lead to avoid a runoff.

With about 95 percent of the votes counted, election officials said Mr. Morales received 46.8 percent of the votes, while his closest rival, Carlos Mesa, won 36.7 percent. To avoid a runoff, the incumbent needed a 10-percentage-point advantage.

Preliminary results released hours after polls closed on Sunday showed a far tighter margin between the two leading candidates, an outcome that appeared to make it certain they would face off in a runoff in December.

Manuel González, the head of the election observer mission dispatched by the Organization of American States to monitor Bolivia’s vote, said on Monday night that he was “profoundly concerned” by the “drastic” reversal in the vote results.