TALLINN, Estonia (AP) — An opposition politician who ran against authoritarian Belarusian President Alexander Lukashenko in the controversial 2020 presidential election has been arrested in Minsk, a human rights group said Thursday.

Andrey Dzmitryeu, a 41-year-old activist who heads the Tell the Truth movement, was seized by security forces late Wednesday near his home in the Belarusian capital, the Viasna center reported.

The reason for the arrest and the charges against him are still unknown. Dzmitryeu is being held at the notorious Okrestsina Detention Center, where human rights activists say political prisoners have been tortured. Belarusian authorities declined to comment on the reported detention.

Belarus was shaken by huge anti-government protests after the disputed August 2020 reelection of Lukashenko, which the opposition and the West denounced as having been rigged. Belarusian authorities responded to the demonstrations with a major crackdown that saw more than 35,000 people arrested, thousands beaten by police and dozens of media outlets and nongovernmental organizations shut.

Running against Lukashenko, Dzmitryeu finished fourth in the election with 1.2% of the vote, according to the official results. During the election campaign, the politician spoke in support of Sergei Tikhanovsky, Viktar Babaryka and Valery Tsepkalo, who were barred from running in the election.