Rights activist Tan Zuoren , whose investigation of shoddy school construction in Sichuan and remarks on the 1989 Tiananmen crackdown angered mainland authorities, went on trial yesterday for 'inciting subversion of state power'. The hearing lasted just three hours. The court rejected all evidence submitted in defence of the 55-year-old writer and all witnesses Tan's lawyer had planned to call. One key witness, fellow activist Ai Weiwei , said he and other Tan supporters were roughed up by police and detained ahead of the trial. Hong Kong journalists were also prevented from covering the trial, with a Now TV reporter and cameraman held by police on a 'tip-off' they had drugs hidden in their hotel room. The trial has drawn attention across the county, with Mr Ai and other rights advocates flying to Chengdu to plead Tan's case. Hundreds of parents whose children were killed by collapsed school buildings in last year's magnitude-8 earthquake also gathered outside the Chengdu Intermediate Court to show their support for Tan. Mr Ai, an activist who embarrassed the authorities with his own campaign to count the children who died in the earthquake, was expected to serve as a witness for Tan's defence. Instead, he and 11 other rights activists were taken away from their hotel before the trial. 'Some people knocked on my door and ordered me to open up. They claimed to be police. I asked them to show their identity and they just kicked down the door. When I asked them again to show their identity, they punched me on my face,' said Mr Ai, who suffered swelling and bruising on his right cheek. 'The trial began with me, a witness, being detained by police for no reason ... They showed no respect for civil rights and the rule of law,' Mr Ai said. He and the other activists were not released until noon, after the trial ended. The authorities gave no explanation for their detention. Hong Kong media organisations condemned the detention of the journalists. The female reporter and cameraman were stopped by police in front of their hotel as they were about to leave for the trial. Saying they had received a 'tip-off' there were illegal drugs hidden in the journalists' rooms, officers detained the pair and seized their identity documents. They were released more than six hours later, after a search of their rooms found nothing suspicious. The reporters were also made to erase a video tape. The Hong Kong Journalists Associated said the drug allegations were groundless and apparently an excuse to stop reporters from covering a sensitive case. The Hong Kong News Executives' Association expressed similar concerns and has asked the central government to investigate. Only Tan's wife and elder daughter were allowed to attend the trial. The wife said Tan pleaded not guilty and insisted on his innocence. Defence lawyer Xia Lin said the prosecutor cited Tan's earthquake probe, an essay on the June 4 crackdown and e-mail exchanges with exiled student leader Wang Dan as the basis for the charge. 'Mr Tan was also accused of giving telephone interviews to hostile overseas media and making remarks that seriously damaged the image of the Communist Party and government,' Mr Xia said. No ruling was handed down.