The new law, approved by parliament last month, does not specifically require Internet sites to be registered, but allows their regulation to be overseen by government decisions.
The Organization for Security and Cooperation in Europe, the continent's leading rights watchdog, called for rejection of the law before its passage.
Independent journalists in the country of 10 million had expressed fears that web sites could be closed down.
"All talk about Belarus introducing restrictions on the Internet is just sheer stupidity," said Vsevolod Yanchevsky, presidential adviser responsible for ideology.
"The authorities feel strong enough not to be afraid of anything, including biased ideas," Yanchevsky said. "On the contrary, it is in our interest to have free development of the Internet and no restrictions. The Internet will be free in Belarus."
Since Lukashenko came to power in 1994, many independent publications have been closed down, leaving the Internet as the chief means of information on the country's small, and often divided, liberal and nationalist opposition.
State media in the country, wedged between Russia and three European Union states, report at length on the president's activities and heap lavish praise on his initiatives. Opposition figures are given little air time apart from brief spots, as required by law, during election campaigns.
Lukashenko, his tough stand on dissent and generous state subsidies are broadly popular, particularly outside the capital.
But the president remains barred from the United States and European Union on grounds that he rigged his 2006 re-election.
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