Belarus President Alexander Lukasheneko faced a challenge to his election victory on Tuesday from international critics and protesters who camped out in the capital overnight accusing him of rigging the count, Reuters reported.
Lukashenko, in power since 1994 and criticized in the West for authoritarian Soviet-style rule, swept back into office on Monday with an official tally of 82.6 percent.
Nearest rival Alexander Milinkevich, with 6 percent, called the poll fraudulent, a view shared widely in the West. The result, never in doubt given Lukashenko's control over much of public life and media, put Washington and Moscow at odds.
Several hundred protesters defied warnings by Lukashenko's state security services and camped out in tents in Minsk's October Square in an action reminiscent of the highly organized 2004 "Orange Revolution" in Ukraine.
Supporters brought sleeping bags, food, hot drinks and blankets to them.
Witnesses said riot police were stationed in sidestreets near the square but there was no sign of any action against the unsanctioned rally, summoned by Milinkevich to demand a rerun of the election and denounce Lukashenko's human rights policies.
"We must stay here permanently. We must stay here until the victory. It is our square. It is our country," Milinkevich told the crowd to chants of "Freedom" and "Long Live Belarus."
About 500 people waved flags banned by Lukashenko. Some people danced to blaring music to keep warm on a freezing morning, and more started to trickle into the square as transport services resumed.
The opposition, demanding a new election in July, called for people to mass at the square for a rally on Tuesday night.
Lukashenko, who vowed in the election campaign to "wring the necks" of those who threatened public order, said his victory marked the failure of an opposition bid to mount a pro-Western coup. He says his rule has spared Belarus the social turmoil and hardship that has befallen other former Soviet republics.
On Monday, up to 7,000 protesters gathered in the square, compared with 10,000 after polls closed on Sunday evening.
Lukashenko, as well as observers in the West and Moscow, will clearly be watching to see if the protests, unmatched in recent years, regain momentum.
Russian President Vladimir Putin, for whom the rise to power of pro-Western governments in Georgia and Ukraine underscored dwindling influence in former Soviet areas, congratulated Lukashenko.
The United States, which last year described Lukashenko as "Europe's last dictator," said the election had been conducted in a "climate of fear."
"We support the call for a new election," said White House spokesman Scott McClellan.
Tightly controlled state television had described the Minsk rally on Monday as a "crowd of drunken youngsters."
Lukashenko, 51, renewed charges his rivals had planned a new pro-Western revolt.
"Let me say that the revolution that so many people talked about and some were preparing has failed and it could not be otherwise," he told a news conference.