Security forces in Belarus have arrested hundreds of people who protested against the result of the country's presidential election.
At least six presidential candidates were among those detained - some reportedly beaten by police.
The EU and the US condemned the crackdown.
But President Alexander Lukashenko, who was re-elected for a fourth term with almost 80% of the vote, accused opposition supporters of "banditry".
"There will be no revolution or criminality in Belarus," he told a televised news conference in Minsk.
Mr Lukashenko also praised the actions of the police on Sunday, saying they had stood in the face of acts of "barbarism and destruction".
Injured opposition candidate Vladimir Neklyaev. Photo: 19 December 2010 Opposition candidate Vladimir Neklyaev was injured and later arrested in hospital
Several hundred people were detained when police dispersed at least 10,000 anti-Lukashenko demonstrators in central Minsk, police spokesman Konstantin Shalkevich said.
The demonstrators tried to storm a government building, but were pushed back by riot police.
Dozens of protesters were injured in clashes after being beaten with batons, according to eyewitnesses.
Observers from the Organisation for Security and Co-operation in Europe (OSCE) called the election "flawed", saying it fell well short of democratic standards.
The EU's foreign policy chief, Baroness Catherine Ashton, demanded the immediate release of the detained opposition leaders.
'Snatched from hospital'
At least six of the nine presidential candidates were among those arrested. Several of them were beaten and injured, their aides said.
Opposition candidate Vladimir Neklyaev was forcibly taken from hospital, where he was being treated after he had been badly beaten by police during their dispersal of a rally by some 200 of his supporters.
One of Mr Neklyaev's aides said men in civilian clothing had wrapped the candidate in a blanket and carried him outside, while his wife screamed, locked in a neighbouring room.
There will definitely be political changes... but no change of power in Belarus"
End Quote Alexander Lukashenko President of Belarus
The US embassy in Minsk said Washington condemned the beating and detention of presidential candidates and called on the authorities in Minsk to exercise restraint.
The EU High Representative, Baroness Ashton, regretted that "last night's events do not reflect the relative progress we had noted so far in the pre-election period".
The interior ministry of Belarus accused the opposition of trying to destabilise the country.
Opposition groups have asked protesters to come back to central Minsk later today to continue the demonstrations against what they say is a rigged election result.
The official results announced early on Monday gave President Lukashenko 79.7% of the vote.
This will ensure the authoritarian leader's fourth term in office.
During his presidency, the former Soviet republic has never held a poll seen as fair by international monitors.
However, the election campaign itself was much freer than in the past, correspondents say.
'Read our laws'
But Mr Lukashenko had earlier warned his opponents against organising rallies as he cast his vote.
"What is awaiting supporters of the protest - read our laws. Everything will be in strict accordance with the law.
"Don't worry, nobody is going to be on the square tonight," the president added.
Police had also warned they would crack down hard on any protests.
During the election campaign, state television for the first time aired a debate among the contenders opposing the president.
Mr Lukashenko - who remains popular among large sections of the population - did not take part in the discussion.
The authorities also allowed activists to collect signatures during the election campaign, perform protest songs and read anti-government poetry.
Despite this, many in Belarus believe that the election day result has already been pre-ordained and the political thaw is merely window-dressing, the BBC's David Stern in Minsk reports.
Mr Lukashenko, who denies the opposition's claim, has said he is not planning to leave, whether by the ballot box or other means.
Asked by reporters last week if the vote would bring any political changes, he said: "There will definitely be political changes. I am sure you meant political changes in general, but no change of power in Belarus."
Are you in Belarus? Did you witness the demonstration? What is your reaction to the election results? You can send us your comments using the form below:
Send your pictures and videos to email@example.com or text them to 61124 (UK) or +44 7725 100 100 (International). If you have a large file you can upload here.