TALLINN, Estonia (AP) — An activist hacker group claims to have infiltrated computers at the country’s largest fertilizer plant to pressure the government to release political prisoners. The state-run Grodno Azot plant has made no comment on the claim by the Belarusian Cyber-Partisans group to have caused damage including destroying backup systems and encrypting internal mail, document flow and hundreds of personal computers. However, the company’s website has been unavailable since Wednesday, the day the group claimed the attack. Group coordinator Yuliana Shametavets told The Associated Press from on Friday that because the plant works with dangerous substances including ammonia the attack was designed to affect only documentation. The group posted photos on social media that it it claimed showed screens of compromised plant computers. Grodno Azot, with about 7,500 employees, is a key producer in the country, whose economy relies heavily on chemical industries. A harsh crackdown on the opposition in Belarus began after protests swept the country in August 2020 in the wake of presidential elections whose disputed results gave authoritarian leader a sixth term in office. Human rights activists say some 35,000 people were arrested in the course of the crackdown and that there are nearly 1,400 political prisoners behind bars today. They include many of the country’s most prominent opposition figures and Nobel Peace Prize laureate Ales Bialiatski, founder of the Viasna human rights group. The 2020 protests were the largest and most sustained show of dissent in Belarus since Lukashenko came to power in 1994. Workers struck in protest at several major plants, including Grodno Azot. Cyber-Partisans said its claimed hack was punishment for “bullying, pressuring & conducting political repression against the company’s employees.”