KYIV, Ukraine — A human rights group said Thursday that authorities in Belarus have brought more than 900 criminal cases carrying potential yearslong prison sentences against opposition figures and protesters in connection with the country's challenged presidential election and the anti-government demonstrations that followed.

The tally released by the Viasna human rights center underlines the harsh response to dissent under President Alexander Lukashenko, who has ruled Belarus since 1994 and claimed victory in last month's election.

The charges in the cases include participating in or plotting riots and violence against police, Viasna said. The most serious offense is punishable by up to 15 years in prison.

Protests, some attracting more than 100,000 people, have rocked Belarus since the Aug. 9 election that official results say gave Lukashenko a sixth term in office but that opponents and some polls workers claim were manipulated.

Even before the protests, the government took extensive actions against opposition activists. One aspiring challenger was jailed and another candidate fled to Russia fearing imminent arrest.