Minsk - Belarus' authoritarian President Aleksander Lukashenko was running for a record fourth term in office in presidential elections on Sunday and was widely expected to win.
Lukashenko, a former collective farm boss, vowed he would defeat his nine challengers without tampering with the electoral process.
But his critics have accused him of ordering police to arrest opposition activists and forcing state-controlled media to support him.
Police in the capital Minsk and outlying cities detained more than a dozen opposition activists on the eve of the election, according to independent news reports.
Vitaliy Rymashevskiy, a campaign worker for the opposition candidate Yuriy Klimovich, told the Belapan news agency that police in the city of Gomel arrested him and charged him for swearing in public.
He denied the charge, claiming his detention was part of a government intimidation campaign, according to a Belapan report.
Law enforcement officials have repeatedly warned that anti- Lukashenko demonstrations planned by the opposition in central Minsk after polls close are unsanctioned and will be broken up by force.
Opposition leaders have vowed to go ahead with Sunday evening protests against electoral fraud and Lukashenko's expected victory.
More than 1,000 international observers led by a 490-member delegation from the Organisation for Security and Cooperation in Europe were in the country to monitor the vote.
Pro-democracy groups have alleged that Lukashenko's government pushed early ballot casting, which took place outside the observation of monitors, with the intention of falsifying the Sunday ballot counts.
Almost one in four Belarusians had cast early ballots by election day, according to data compiled by the Central Election Commission.
Lukashenko has rejected claims the election will be fraudulent, saying his real support in the country is so substantial that he has no need to fix the vote in his favour.