Early voting is set to begin in Belarus, five days before a presidential election officially due to take place on Sunday.
Opposition groups say early polling is an opportunity for President Alexander Lukashenko to rig the vote.
Main opposition candidate, Alexander Milinkevich, has urged people to stay away, saying votes will be stolen.
The president, who has been in power for 12 years, changed the constitution to allow his bid for another term.
Opinion polls suggest President Lukashenko is on course for a landslide victory, as was the case in his previous campaigns.
The Belarus authorities often open polling stations several days in advance of elections, allowing people to vote early.
The procedure is seen by observers as a way of manipulating polls. But Belarus authorities have defended it.
"Ahead-of-schedule voting is practised all over the world," Nikolai Lozovik, Secretary of the Central Electoral Commission, told Itar-Tass news agency.
"Any citizen who is entitled to vote may come to the polling station and cast a ballot ahead of time without giving reasons," he said.
International observers will monitor the election but critics believe they will not be fair.
The United States has described Belarus as Europe's last dictatorship.