By STEVEN LEE MYERS
MOSCOW, March 2 - Security officers in Belarus today arrested and beat a candidate running against President Aleksandr G. Lukashenko, raising tensions ahead of a disputed presidential election scheduled for March 19.
Aleksandr V. Kazulin, an opposition candidate in Belarus, was taken into custody by security officers while attending a political convention in Minsk.
The challenger, Aleksandr V. Kazulin, was released more than eight hours later, but not before his arrest prompted protests, scuffles with police and dozens more detentions during a series of confrontations in the capital, Minsk.
Gunfire erupted near a police station where he was taken, as police officers fired warning shots in an attempt to stop a car carrying his supporters and a photographer, according to the candidate's spokeswoman and the election observer mission of the Organization for Security and Cooperation in Europe.
"Today it was shown that the president is extremely afraid of his own people," Mr. Kazulin said in a telephone interview after his release this evening. "We call on the world community to issue a strict protest against the fact that in the center of Europe a dictatorship is metastasizing."
The arrests marred an election campaign that the United States and Europe have already criticized as dubious given the pressure Mr. Lukashenko's government has exerted against his presidential opponents, their supporters and members of advocacy groups.
They came a day after the country's security chief warned in televised remarks that opposition leaders intended "to seize power by force" by staging violent election protests with the support of foreign nations, including the United States. Mr. Lukashenko reiterated that charge on today in a long address to the All-Belarussian People's Congress, a gathering of supporters designed to endorse his presidency.
"The Belarussian people have realized through their own experience that only dark forces are behind revolutions, regardless of the revolution's color," he said in televised remarks as transcribed and translated by the British Broadcast Service, referring to the popular uprising known as the "orange revolution" that followed fraudulent presidential elections in neighboring Ukraine in November 2004.
The arrest brought new foreign criticism against Mr. Lukashenko, who has ruled Belarus with an increasingly iron fist since he was first elected in 1994, jailing political opponents, closing private advocacy organizations and suppressing independent newspapers.
The O.S.C.E.'s Office for Democratic Institutions and Human Rights, which has sent observers to monitor the election campaign, said in a statement that the arrest followed a pattern of government pressure that reflected "a serious deterioration in the campaign atmosphere."
President Bush's national security adviser, Stephen L. Hadley, said today that the incident underscored the need for greater international condemnation of the government's behavior in advance of the election.
"We would like it to be free and fair, and a prerequisite of a free and fair election is that you don't beat up opposition candidates or opposition supporters and thrown them in jail," he said in a briefing with reporters in New Delhi, where Mr. Bush was traveling, according to a White House transcript. "And we think that there is not enough outrage and international attention on Belarus generally - in the run-up to this election, in particular."
Mr. Kazulin was arrested, along with three campaign aides, after trying to register as a delegate for the congress this morning. The police barred him from entering a building where the registration was taking place, sparking a brawl that left Mr. Kazulin badly beaten, his face bruised, his lip broken and his shirt bloodied, according to his spokeswoman, Nina Shidlovskaya.
Several others were also beaten, including a Russian journalist for the local edition of Komsomolskaya Pravda and a television cameraman for Reuters, while the police seized and destroyed cameras and film of the initial arrests.
The police detained at least 20 people, including Mr. Kazulin's lawyer and journalists, outside the police station where he was eventually taken.
By evening, some had been released but not all, Ms. Shidlovskaya said. The atmosphere in the city remained tense into the night, as riot police confronted and arrested dozens more around the city and during a campaign rally held by the leading opposition candidate, Aleksandr Milinkevich, according to news reports and opposition spokespeople.
Mr. Kazulin said that he had been charged with disorderly conduct and hooliganism, though it was not yet clear when he would face a trial.
Mr. Kazulin, a former education minister and rector at the Belarus State University, is less well known than Mr. Milinkevich, who was elected as a unified democratic opposition candidate by a disparate array of parties and organizations. Mr. Kazulin, however, has emerged as fiercer and more confrontational than Mr. Milinkevish during the campaign.
Aligned more with Russia, which has tacitly supported Mr. Lukashenko, Mr. Kazulin has harshly denounced the government's actions and provoked confrontations during official events, like a ceremony last month to register candidates. During his detention today he smashed a framed portrait of Mr. Lukashenko at the police station.
He vowed to continue his campaign. "The country is rising up," he said in the telephone interview. "We will liberate Belarus from Lukashenko's yoke."
A fourth candidate, Sergei Gaydukevich, is a member of Parliament and leader of the Liberal Democratic Party who has allied himself with Mr. Lukashenko.
Mr. Milinkevich, who has risen significantly in independent polls, though he still trails Mr. Lukashenko, denounced Mr. Kazulin's arrest as "a flagrant violation" of the law and derided the election as "a farce."
"They realize that they cannot win an open, competitive struggle, so they do not stop violating the law and repressing their opponents."