Last week's jailing for six years of veteran dissident Wang Rongqing for "subversion of state power" was more than just another unpleasant instance of official vindictiveness, supporters and human rights groups say. China is facing a turbulent year of deepening economic hardship, social unrest, and tense anniversaries. The authorities are running scared. And so they made an example of Wang.

The diagnosis seems to apply to other prominent dissidents, also feeling the heat as economic boom times fade and political jitters increase. Liu Xiaobo, a noted literary scholar, has been held without charge since 8 December. His apparent offence was supporting a new campaign for political and legal reform known as Charter 08.

According to Amnesty International, Liu's family does not know where he is, he has no access to a lawyer, and he has yet to be charged or brought before a court. "The use of such detention ... is arbitrary and in violation of international human rights standards, including the rights to liberty, security of person, and fair trial," said Amnesty's Roseann Rife.

Charter 08 was signed by 303 Chinese scholars, lawyers and officials, many of whom have reportedly since been harassed or placed under surveillance. China expert James Pringle says the campaign, modelled on Vaclav Havel's Charter 77 in cold war Czechoslovakia, "is the first real opposition to the Communist leadership since Tiananmen Square" and is widely seen as "a threat to the party's monopoly on power".

Writing in the Wall Street Journal, Havel said more than 5,000 people had since defied official hostility and added their names to the charter. He warned China against making the same mistake as the Czechoslovak authorities in choosing repression over the chartists' offer of "engagement, dialogue and debate".

Another leading dissident, environment and human rights activist Hu Jia, meanwhile remains incarcerated after being jailed last year for "inciting subversion". The European parliament awarded him the Sakharov prize for freedom of thought last month. But concerns expressed to China's president, Hu Jintao, by Human Rights Watch and Physicians for Human Rights about Jia's health and treatment in prison have gone unheeded.

Hardening attitudes to dissent aside, rising official anxiety about challenges to Communist control also appear to form the subtext to a recent crackdown on internet websites. The reimposition of censorship of foreign sites, such as the New York Times, has been followed by the closure of 91 sites and threats against search engines such as Google and Baidu. While the authorities' stated aim is to curb pornography and other "vulgar" content, online political criticism also seems to be a target. One blogger, Luo Yonghao, said his site had been shut because the government said it contained "political harmful information".

Analysts link these developments to a string of potentially disturbing anniversaries this year. They include the 50th anniversary on 10 March of the Tibetan uprising, the 20th anniversary on 4 June of the suppression of the Tiananmen Square pro-democracy protests, the 10th anniversary on 22 July of the banning of the Falun Gong movement, and the 60th anniversary on 1 October of the founding of the People's Republic.

All these events are controversial in their own way and all could become magnets for trouble. In normal times, that might not matter quite so much. But social conditions inside China are anything but normal as the global recession bites.

Official figures indicate up to 10 million rural migrants have already lost their jobs as southern factories close, annual growth falls, and exports decline for the first time in nearly a decade. In July, 7 million new graduates will place additional pressure on a contracting jobs market. Add to this standing grievances about party corruption, misgovernance, and the widening wealth gap between rich and poor, and commentators say the risk of widespread social unrest becomes significant.

"In 2009 Chinese society may face even more conflicts and clashes that will test the governing abilities of all levels of party and government," Xinhua news agency reporter Huang Huo told the officially-sanctioned Outlook magazine this month. "Without doubt we are now entering a peak period for mass incidents" (meaning protests ands riots). And these "incidents", the magazine suggested, were becoming increasingly politicised.

Speaking on the record, Chinese spokesmen play down the prospect of spreading unrest. "We have the ability and the confidence to ensure the economy's relatively fast growth and to ensure social stability," said the foreign ministry's Qin Gang. All the same, Outlook magazine's unusually candid, public warning is seen as an alarm call directed at governing cadres.

The (uncensored) message: in a difficult year, persecuting dissidents and closing websites may not be enough to save China's rulers from a painful reckoning with China's over-pressured and under-represented masses.