Belarusian security authorities have raided the homes and offices of journalists and human rights activists, following months of opposition protests.
Police searched the offices of the Belarusian Association of Journalists (BAJ) and the Viasna human rights centre in Minsk, detaining around 25 people, according to activists.
The leader of the BAJ, Andrei Bastunets, was one of those initially arrested. At least ten people have reportedly been remanded in custody facing criminal charges.
"This is the largest crackdown ever on journalists and rights activists Europe has ever seen," said Boris Goretsky, the association's vice president.
"There have been more than 400 detentions of journalists over the last six months, and the authorities aren't going to stop at that."
The apartments of several other trade union leaders across Belarus were also raided on Tuesday, where IT equipment and documents were seized.
"This is an attempt to intimidate journalists and human rights activists who have been telling the world about the unbelievable scale of repressions," said Viasna activist Valiantsin Stefanovich.
Belarus has been rocked by anti-government demonstrations since the disputed election result on August 9, which saw President Alexander Lukashenko claim a sixth term in office.
The exiled main opposition candidate, Sviatlana Tsikhanouskaya, and her supporters have dismissed the result as rigged.
Authorities have responded to protests, the biggest of which attracted up to 200,000 people, with a sweeping crackdown. According to human rights advocates, more than 33,000 people have been detained since the protests began, and thousands were brutally beaten.
The crackdown has prompted sanctions from the European Union but Lukashenko has refused to step down.
In a statement on Telegram, Belarus' Investigative Committee said Tuesday's raids were carried out on "organisations posing as human rights defenders" which had financed the protests.
Those detained are suspected of organising or participating in actions that "grossly violate public order", the Committee added.
Tsikhanouskaya has denounced the raids as a "real state crisis" and added that "all Belarusians are in danger".
"We have already transmitted information to the European Union and the UN Human Rights Council demanding to take action," she added on Telegram.
The raids came as two journalists from the Poland-based television channel Belsat are on trial in Minsk, facing up to three years in prison for reporting from the opposition protests.
Last week, Lukashenko held a two-day "People’s Assembly", saying he had defeated a foreign and opposition "Blitzkrieg" against his regime.