Both the official exit polls and the chief election official later predicted he would get even more.
The authoritarian leader faced no serious competition in the election, which was boycotted by the opposition.
About 100 opposition supporters held a protest march after polls closed to show their discontentment, but the demonstration ended peacefully.
"Lukashenko himself set the election, set his competitors and set the per cent that he would receive," said Vadim Venyarsky, 34, who was among the protesters.
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Lidia Yermoshina, the head of the Central Election Commission, said results from voting in hospitals and on military bases, even though they represented only 1 per cent of voters, already showed his overwhelming win.
"These data give the idea, the picture and tendency of the whole society: 89 per cent voted for Alexander Lukashenko," she announced as soon as polls closed.
Even before polls opened in the former Soviet republic, the Central Election Commission announced that 36 percent of the 7 million registered voters had cast their ballots during five days of early voting.
"It is very unusual for us to find that a country has an election so many days," James Walsh, who heads the delegation from the Organization for Security and Cooperation in Europe's Parliamentary Assembly, told The Associated Press. "Most democracies have a challenge in getting its citizens ... To come out and vote."