Authorities in the southern province of Guangdong have detained a man who ran a number of social media chat groups, in a nationwide crackdown on free speech ahead of a five-yearly congress of the ruling Chinese Communist Party. A team of cybersecurity police visited the home of Zhang Guanghong in Yuexiu district of Guangdong's provincial capital Guangzhou on Wednesday even in connection with posts made to groups on the popular social media platform WeChat. "He was detained recently because of what had been posted," a friend of Zhang's told RFA. "There is huge political pressure at the moment because of the 19th Party Congress, and many people are worried about being arrested, so we daren't speak out," the friend said, declining to comment further. State security police and local officers from the Meihua Street police station searched Zhang's home, seizing four cell phones and a server. He was held for 24 hours before being released, but repeated calls to his mobile phone rang unanswered on Thursday. An officer who answered the phone at the Meihua Street police station declined to comment when contacted by RFA on Thursday. "I don't know[where he is]," the officer said. A friend of Zhang's surnamed Lin said he hasn't been in touch since. "He told us online that the police had come looking for him, and since then he hasn't posted again," Lin said. "They burst in on him while he was having dinner at a friend's house, and confiscated the friend's phone to stop them from posting about[Zhang's] detention." "I'm guessing that they have taken his cell phone away, and he can't send out any messages," he said. Rights lawyer Yu Wensheng said the detention is linked to a massive nationwide clampdown in the run-up to the party congress. "This definitely has to do with stability maintenance measures for the 19th Party Congress," Yu said. "As far as they are concerned, the law is a blank slate ... they don't abide by the law, but that's all I have to fight with." "There is very little we can do right now ... to protect people's rights," he said. Scaling the Great Firewall Guangzhou cybersecurity police also questioned a human rights activist after she bought a router enabling her to scale the "Great Firewall" of government internet censorship. Zhang Weichu said several police officers came to her home on Wednesday morning after she bought the router, and telling her she had violated the country's cybersecurity law. "Three plainclothes and one uniformed officer knocked on my door ... and asked if this was the apartment where there was a router for circumventing the Great Firewall," Zhang told RFA. "They said circumvention routers were illegal, and that they were going to confiscate it," she said. Zhang said she had insisted that they produce some form of official documentation, such as a receipt, before they could take it. "So they said they were issuing a verbal summons, to which I replied that I wanted to see it in writing," she said. "They even threatened me, saying it was against the cybersecurity law, but they couldn't tell me which article." She said the police had identified themselves as coming from the cybersecurity team of the Guangzhou police department. Zhang had bought a KF router licensed for sale in China to companies and organizations needing to do business online with clients and customers overseas. Online sales copy for the router said it offers an uncensored internet connection via more than 100 servers located outside China, claiming to be cheaper and more reliable that a virtual private network (VPN). "KFRouter allows to use Google, Facebook, YouTube, Twitter, INS and so on as old days in your country," the sales pitch says, in a reference to overseas social media sites currently blocked by the ruling Chinese Communist Party. Zhang's sister Zhang Wuzhou said she had only used the router once before police came knocking. "It's unbelievable that if an ordinary person goes on Google once, they get questioned by police," she said. "These are websites that the whole world can access."