Mainland journalists' microblogs are shaping up as the next target of a continuing crackdown on internet 'instruments of subversion'. The microblog service run by Sina, one of the mainland's four main commercial portals, had received orders to verify all accounts of journalists working in the traditional media, one media analyst close to Sina's middle-management said. He added Sina was trying to negotiate with the authorities and reach a compromise. A Sina editor said only influential journalists' Sina microblog accounts were verified at present. All mainland microblog websites were asked to exercise self-discipline recently, with the Sohu and NetEase microblogs closing down for a couple of days, after the Bluebook of New Media by the Chinese Academy of Social Sciences branded internet networking tools such as Facebook and Twitter as potential instruments of subversion. Microblog searches now return fewer results, and for sensitive topics no results at all. Facebook and Twitter were both shut down on the mainland last year. Media analyst Song Shinan said tighter control of journalists' microblog accounts could be expected. 'Journalists have strengths in news sources and opinions. They sometimes publish information censored by the media outlets they work for. It would be very easy to monitor their entries after account verification,' he said. 'Microblogging is the hardest form of communication to control and is most influential as information spreads most quickly.' More than 80.65 million internet users on the mainland used microblogging services in May, up by almost 50 per cent from March, according to statistics from iResearch, an information technology market research company. Recent months have seen tighter control over the internet. Measures have included the push for real-name user registration, a crackdown on unhealthy content, appeals for self-discipline and the shutting down of microblogs and blogs. State Council Information Office director Wang Chen said two months ago that the mainland was on track to implement the real-name registration system. More than 100 Sohu blogs by influential scholars, media practitioners and lawyers have been killed off since Wednesday. 'It's not targeting the content but the people,' said blogger and scholar Wu Zuolai, whose closed-down blog had published nearly 1,000 entries and attracted more than 2 million page views over the past five years. 'Thousands of items that are cultural resources have disappeared.' A blogger was told by a friend working at Sohu that it had received a list from the 'top' naming outspoken bloggers. Another blogger whose blog was killed, Yao Yuan, said: 'It's unbearable. It's a very serious case of killing so many blogs at the same time.' He has drafted a protest letter and is seeking signatures from other bloggers. 'If we are silent, it will become common practice to use websites as scapegoat for the killing of the freedom of expression entitled by the Constitution and the White Paper of the internet in China,' he wrote.