Belarussian police, meanwhile, rounded up and detained demonstrators at a new protest nearly two months after Lukashenko's disputed re-election - this time against the disappearance of prominent public figures.
Artur Finkevich acknowledged painting some slogans on walls, including "Enough!" and "We want a change".
He had initially been charged with malicious hooliganism and damaging property worth more than $15,000 in 17 cases directed against Alexander Lukashenko, the president.
Graffiti is a common form of protest in Belarus, where opposition newspapers have been closed down and independent art forums harassed since Lukashenko came to power in 1994.
Prosecutors had wanted a jail sentence of seven to 12 years. Total damage was assessed in the end at no more than $1,000.
Tatyana Revyako, a human rights specialist who was in court, said: "We, naturally, believe this sentence is political and intended to intimidate young people.
"The judge threw out the article on mass damages as no documented proof was provided for this sum."
In the evening, several dozen activists defied a police ban to gather in Minsk's October Square to demand explanations for four disappearances. Many carried portraits of Yuri Zakharenko, a former interior minister who vanished in May 1999.
Several protesters were detained.
Belarus has known post-election
tensions (file photo)
The Belarussian opposition, long cowed by tough legislation against dissent, staged unprecedented protests to denounce the vote - dismissed by the president's rivals and the West as rigged.
Opposition figures, including Alexander Milinkevich, who came second in the poll, were jailed for up to 15 days for public order offences and are due to be released this week.
The European Union has slapped a visa ban on Lukashenko and 30 officials in response to the election results. Last week, Dick Cheney, the US vice president, repeated Washington's contention that Belarus was the "last dictatorship in Europe".