By MICHAEL SCHWIRTZ
MOSCOW - The United States and the European Union on Monday imposed sanctions against President Aleksandr G. Lukashenko and scores of other officials in Belarus for a broad crackdown on the opposition following fraudulent presidential elections late last year.
Under the sanctions, Mr. Lukashenko and others will be prohibited from entering the United States or the European Union, and any of their assets held in those territories will be frozen. In addition, Washington adopted measures against one of Belarus's largest government-owned companies.
The Foreign Ministry in Belarus immediately condemned the decision, vowing a "proportionate and adequate" response, according to a statement on its website.
American officials and their European allies said they were compelled to act amid a relentless campaign of intimidation in Belarus against government opponents that has continued since the police violently dispersed a large protest against Mr. Lukashenko's accession to a fourth term in last year's elections.
At the protest, held as polls closed on December 19, thousands of demonstrators called for Mr. Lukashenko's ouster, accusing him of stealing the elections and transforming Belarus, a former Soviet republic, into a dictatorship. Over 600 people, including seven of the nine presidential candidates opposed to Mr. Lukashenko, were arrested.
Western officials had said Mr. Lukashenko and his government could avoid punishment by releasing all jailed political prisoners and ending the crackdown.
Mr. Lukashenko released at least seven opposition figures in recent days. But at least two dozen opposition leaders, including three former presidential candidates, remain in jail, facing up to 15 years in prison for their roles in the protest.
The United States and the European Union imposed less stringent sanctions after a crackdown on opposition forces following elections in 2006. The United States, which has not had an ambassador in Belarus since 2008, has kept those sanctions in place. The European Union, however, suspended them amid promises by Mr. Lukashenko to ease his authoritarian grip.
The president had indeed appeared to be experimenting with the trappings of democracy ahead of the recent elections, allowing candidates to campaign across the country and even hold live debates on government-controlled television (though he himself did not participate).
The European Union had offered investment opportunities and about $3.5 billion in aid in exchange for elections that independent observers could deem free and fair for the first time.
But Mr. Lukashenko failed to comply. After the protest, which he claims was part of a Western-backed coup attempt, he began a campaign of repression that even seasoned opposition figures say has exceeded anything in the president's 16-year rule.
Six weeks after the election, the security services, still called the K.G.B. in Belarus, continue to regularly round up those suspected of ties to the opposition. Independent media outlets and human rights organizations have been shut down, their computers and documents confiscated. Those determined to have been present at the protest have been jailed for up to 15 days, rights groups say.
The new sanctions are more far-reaching than any imposed earlier, taking aim at many more officials. The European Union has published a list of 157 officials, 117 of which had not fallen under previous sanctions. In addition to Mr. Lukashenko, the list includes two of his adult sons, the defense and interior ministers and the head of the K.G.B.
Washington and Brussels also vowed to increase financial and diplomatic support for the political opposition and civil society groups.
Mr. Lukashenko has been defiant in the face of punishment and has given vague indications that he would retaliate. Ahead of Monday's decision, he openly mocked the threat of sanctions, saying he would survive them.
In its statement, Belarus's Foreign Ministry decried "interference in the affairs of a sovereign government."
"This undermines trust," the statement said, "and will inevitably lead to actions that will destroy the prospects for the formation of a Europe without dividing lines."
Stephen Castle contributed reporting from Brussels