Belarusian President Alexander Lukashenko has won his fifth term with a landslide 83.5% of the vote.
None of three other candidates in Sunday's election achieved more than 5%. The turnout was 86.75%.
But observers from the OSCE security body said it fell far short of the country's democratic commitments.
There were "significant problems" in the counting and tabulation of votes, the Organization for Security and Co-operation in Europe complained.
Mr Lukashenko, 61, has governed the former Soviet republic almost unchallenged for 21 years.
No veteran opposition leaders stood, as they were not allowed to register. A Belarusian human rights group also said the vote fell far short of democratic norms.
Aleh Hulak, head of Human Rights Defenders for Free Elections, criticised "mass early voting" and "non-transparent vote-counting".
The OSCE's chief observer, Kent Harstedt, said "it is clear that Belarus still has a long way to go towards fulfilling its democratic commitments".
He described the recent release of political prisoners and welcoming of election observers as "positive developments", but said "the hope that this gave us for broader electoral progress was largely unfulfilled".
Dozens of opposition supporters held a protest march in the capital Minsk after the polls closed.
They carried slogans that read "Boycott the dictatorship!" and "Lukashenko - go!"
Earlier Belarusian TV showed Mr Lukashenko casting his vote at one of the polling stations, as his youngest son Nikolai stood by. Nikolai has accompanied his father on numerous public occasions in recent years.
Critics accused the president and his supporters of preventing the main opposition parties from building any public profile and restricting their access to the all-powerful state-owned media.
This year's Nobel Literature Prize laureate, Svetlana Alexievich, has warned that her country is a "soft dictatorship".
She said Mr Lukashenko was a man connected to the Soviet era and was untrustworthy. None of her books has been published in Belarus.
US officials have described Mr Lukashenko as "Europe's last dictator".
However, there have recently been signals - including the pardoning of six opposition leaders - that suggest Mr Lukashenko is seeking to improve relations with the West.
He has hosted several rounds of Ukraine ceasefire talks in Minsk, welcoming EU leaders and ending his diplomatic isolation.
- Belarus, with seven million voters, held its fifth presidential election in 21 years - and each time Alexander Lukashenko won
- The president has not polled less than 75% in any of the five elections
- Of the three challengers, two were regarded as "technical" pro-Lukashenko candidates
- The only woman among them, Tatsiana Karatkevich, was an activist disowned by almost all opposition parties except her own Tell the Truth movement
Last time a presidential election was held in Belarus - in 2010 - seven of the nine presidential candidates were arrested.
One of them was only released this year following widespread international pressure.
The candidates were accused of various offences, including the encouragement of violent protest and attempting to overthrow the state.