Belarus on Monday sentenced at least 20 people to jail for up to 15 days for protesting against the authoritarian rule of President Alexander Lukashenko.

Authorities in the one-time Soviet state arrested nearly 400 people Sunday as the country marked its 1944 liberation from Nazi occupation.

Plain-clothes security officers drifted through the crowd in Minsk that turned out to hear Mr. Lukashenko speak and arrested people whom they said were disrupting his speech by clapping their hands but otherwise remaining silent.

On Monday, some of those arrested appeared in court on charges of hooliganism. Some were convicted and handed sentences of seven to 15 days in jail. Cases against others were put off until Tuesday.

Opposition has grown against Mr. Lukashenko's 17-year rule and the country's worsening economic crisis. He launched a crackdown on the opposition after his disputed re-election in December.

Western governments have decried his crackdown, saying Mr. Lukashenko has shown a disregard for democratic values. The European Union has frozen the assets and imposed travel restrictions against Mr. Lukashenko and more than 150 government officials and close associates of the president.