TALLINN, Estonia (AP) — An opposition politician who ran against authoritarian leader Alexander Lukashenko in the controversial 2020 Belarusian presidential election was arrested in Minsk on Wednesday, a human rights group says.

Andrey Dzmitryeu, a 41-year-old activist who heads the Tell the Truth movement, was seized by security forces 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 re-election of President Alexander Lukashenko, which the opposition and the West denounced as a rigged sham. Authorities responded to the demonstrations with a massive crackdown that saw more than 35,000 people arrested, thousands beaten by police and dozens of media outlets and non-government 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 elections.