The recent banning of six mainland writers from visiting Hong Kong and the barring of two exiled authors from returning to their homeland shows Beijing’s latest wave of control over dissent has extended to independent-thinking intellectuals and writers, some of them say.

Writers prevented from joining the Independent Chinese PEN Centre’s 10th anniversary celebration in Hong Kong on Saturday include scholar Cui Weiping , former Peking University journalism professor Jiao Guobiao , journalist Zan Aizong and lawyer and essayist Zhuang Daohe.

The day after the conference, exiled writers Bei Ling , an American citizen, Ma Jian , a Hong Kong permanent resident based in Britain, and the group’s incumbent president Tienchi Liao – a German citizen, were refused entry to Shenzhen as they tried to cross the border from Hong Kong. They were interrogated separately for over an hour.

Writers’ organisation PEN International said the incident was “an increasingly alarming situation for writers and activists in China”. Four members of the Chinese branch of PEN – including former president and Nobel Peace laureate Liu Xiaobo who is serving 11 years for subversion – are among at least 40 writers imprisoned on the mainland.

Jiao, who lost his job in 2004 after he denounced the party’s control of freedom of speech, said that last year police barred him from leaving home for 49 days and he was required to report his movements to them for more than 200 days.

“I guess the controls will only get tighter and tighter,” Jiao said.

Several writers and academics confirmed independently they had been warned by the authorities in recent months to maintain a low profile and not make public statements.

Bei, whose manuscript on former dissident and ex-Czech Republic president Vaclav Havel was filmed by the police while he was being held, said Beijing’s crackdown on dissent had widened in scope to target writers and intellectuals.

“This is obviously targeted at PEN and is a clear repression of writers and intellectuals who think independently,” said Bei, who wanted to meet his elderly father – whom he had not seen for six years. He said the repression had escalated since Liu received the Nobel prize last October.

Fearing that revolts similar to those in the Arab world could spread to the mainland, the authorities launched a harsh crackdown on government critics in February, leading to the detention of scores of activists, bloggers and lawyers.

Bei cited the persecution of writers such as Liao Yiwu , an author who fled to Germany this month after being repeatedly barred from travelling overseas, this weekend’s barring of mainland writers from coming to Hong Kong and the refusal to allow him to return to the mainland as evidence that the intensity of the repression has increased.

Liao regretted that she and other PEN members could not get into the mainland.

“This is a message that they are very hostile towards PEN and our members … but we’re not afraid and we’ll continue to struggle,” she said.

Several members of the PEN American Centre travelled to Beijing last week but only three of 14 writers invited to a US embassy-hosted forum were able to attend. Other invitees, including blogger Liu Di , were pressured by authorities not to attend.

Rights lawyer Mo Shaoping and writer Dai Qing were unable to meet alone with delegation members, also apparently due to official pressure.