The reported move came amid a mounting campaign by officials to pressure the opposition ahead of the presidential election on March 19.
Iosif Syaredzich, publisher of the "Narodnaya volya" newspaper, said two trucks carrying 250,000 copies were seized at the border late on March 5.
He said the paper had printed a special edition with photographs showing last week's beating of an opposition candidate, activists, and reporters by security agents.
"Narodnaya volya," whose print run is normally around 30,000, is printed in Russia to avoid being shut down by Belarusian authorities.
Authorities have accused the newspaper of unlawful campaigning.
Belarus' authoritarian President Alyaksandr Lukashenka is seeking a third term in the March 19 election.
The Media In Belarus
CPJ Europe and Central Asia Program Coordinator ALEX LUPIS, who had just returned from a trip to Belarus, told an RFE/RL briefing on 15 February that he found conditions that make it almost impossible for journalists to report independently on the campaign leading to the country's 19 March presidential election.
Lupis said the Belarusian government is "criminalizing" independent journalism, and forcing journalists to leave the country, change professions or join the state-controlled media. There is a "Cold War atmosphere" in Belarus, Lupis said, adding that President Alyaksandr Lukashenka makes up the rules of the game. The Internet, he said, is the "last free outlet" where independent journalists can publish, but Russia and Belarus are updating their media laws in order to restrict Internet usage. Numerous journalists with whom Lupis spoke said that they miss the support they used to receive from nongovernmental organizations such as IREX and Internews, which were once active in Belarus.
Lupis believes that the government in Belarus bans independent journalism because it fundamentally "mistrusts its own people."
See these RFE/RL stories on the media in Belarus:
Authorities 'Cleanse' Media Ahead Of 2006 Vote
Click on the image to view a dedicated page with news, analysis, and background information about the Belarusian presidential ballot.