Hu Jia, one of the mainland's most high-profile dissidents, said he was questioned by police for more than seven hours yesterday and warned that he could be detained again if he continues campaigning on behalf of fellow activists. Hu, who was released in June after serving a 3 1/2-year prison sentence on subversion charges, was summoned by police and accused of violating the conditions of his release. Hu was subjected to a year of 'deprivation of political rights' upon his release. Under the terms, he was barred from giving press interviews, protesting or publicising his views. However, he has since posted messages on Twitter calling for the release of jailed dissident Liu Xiaobo and his wife Liu Xia, who is under house arrest; blind legal activist Chen Guangcheng, who is confined to his house with his family and cannot be contacted; and rights lawyer Gao Zhisheng, who was recently sent back to prison after disappearing for 20 months. Hu has also urged his internet followers to show their support to these activists. 'They were targeting the opinions I expressed on the internet, mainly about these three cases,' he said. 'They sternly warned me that if I didn't stop I could be given 15 days of detention ... [but] I told them I have the constitutional right to openly criticise [the government].' When he was released from jail, Hu was warned that if he continued pursuing his rights activities he could be sent back to jail for more than 10 years for being a repeat offender, on the charge of 'inciting subversion of state power'. 'They could charge me again with subversion - I think this is highly possible,' he said. 'But there are so many people in trouble, and their pain is much greater than mine. I can't just ignore them.' Eight policemen went to his home with a search warrant on Wednesday night, interrogated him for 1 1/2 hours and confiscated two computers, he said. Hu told his four-year-old child that the policemen were his friends so she would not be frightened. He said that after being questioned at length, he and his wife Zeng Jinyan were told to return to the police station today for further investigation. Beijing police refused to comment yesterday. Phelim Kine, senior Asia researcher at Human Rights Watch, said 2012 would be 'a fraught year of heightened police surveillance, harassment and detention of high-profile human rights activists and civil society activists in the run-up to this year's leadership change in the ruling Chinese Communist Party'.