Belarus is voting in presidential elections, with the incumbent Alexander Lukashenko is widely expected to win.
Under the authoritarian leader aiming to secure his fourth term, the former Soviet republic has never held a poll seen as fair by international monitors.
However, these elections so far have been much freer than in the past, correspondents say.
But the opposition still plans to hold protests against what they say will be a rigged vote.
Security forces have warned they will crack down on any attempts to stir tension during or after the voting.
Polling stations across Belarus opened at 0600 GMT and will close at 1800 GMT.
Nine challengers are competing with Mr Lukashenko for the presidency.
For the first time, state television aired a debate among the contenders opposing the president, who has governed since 1994.
Mr Lukashenko - who remains popular among large portions of the population - did not take part in the discussion.
The authorities also allowed activists to collect signatures during the election campaign, perform protest songs and read anti-government poetry.
Despite this, many in Belarus believe that the election day result has already been pre-ordained and the political thaw is merely window-dressing, the BBC's David Stern in Minsk reports.
"Lukashenko needs this to show to the Europeans because he needs money from Europe," said Andrei Sannikov, one of the three main opposition candidates.
"The economy is in very bad shape and he needs additional credits," he said.
Mr Lukashenko, who denies the opposition's claim, has said he is not planning to leave, whether by the ballot box or other means.
Asked by reporters last week if the vote would bring any political changes, he said: "There will definitely be political changes. I am sure you meant political changes in general, but no change of power in Belarus."