BEIJING — For Chinese authors who join the international writers’ organization PEN, membership would appear to have very few privileges. Many of its members are subjected to frequent harassment; four of them are currently in prison, including one of its founders, Liu Xiaobo, the essayist and Nobel Peace Prize laureate serving 11 years for subversion. All told, the group counts 40 journalists, novelists and historians imprisoned because of their writings.

On Saturday, the authorities once again demonstrated their displeasure with the organization by barring three writers from joining Independent Chinese PEN Center’s 10th anniversary celebration in Hong Kong. Those prevented from attending were Zhuang Daohe, a Hangzhou lawyer and essayist; Jiao Guobiao, a Beijing journalism professor who lost his job after writing a critique of the Communist Party; and Cui Weiping, a poet and film scholar who was to receive an award on Saturday.

Mr. Jiao, like the others, had bought a plane ticket but was prevented from leaving his apartment by a contingent of security agents. “I don’t know how much longer I can put up with this,” Mr. Jiao said in an interview via Skype on Saturday. “It’s getting worse and worse.”

Although writers who refuse to conform to government restrictions have long been persecuted in China, conditions have worsened since February, when the Communist Party began a wide-ranging crackdown on dissent prompted by fears that the pro-democracy protests in the Arab world could spread to China.

Dozens of rights lawyers and critics have been detained, among them the artist Ai Weiwei, who spent nearly three months in custody. The government has accused Mr. Ai of tax evasion, but conventional wisdom suggests his more urgent crime was the frequent and unvarnished criticism he directed at the Communist Party. Since his conditional release last month, Mr. Ai has been conspicuously silent.

Except for Mr. Liu, the jailed Nobel laureate, most Chinese writers who cross the authorities suffer in relative anonymity. Their works are banned, employment opportunities dry up and their daily movements are constrained by security officials who prevent them from leading normal lives.

Mr. Jiao offered a precise tally of the restrictions on his movements. Last year, he said, he was confined to his home for 249 days. On other days, he was required to receive permission to meet with friends. “On the days I could go out, I had the feeling I was being followed,” he said.

Last year, Ms. Cui was prevented from going abroad to attend a film conference in the United States; the nonfiction writer Liao Yiwu was pulled off a plane that was to take him to a literary festival in Germany. After 17 failed attempts to leave China, Mr. Liao surprised the authorities this month by secretly making his way to Germany, via Vietnam and Poland, and declaring himself an exile.

A delegation from the PEN American Center that came to Beijing last week had a firsthand encounter with the growing stranglehold on dissident writers. On Wednesday, the group invited 14 people to a roundtable discussion on free expression at the American Embassy in Beijing. Only three arrived.

Among those blocked from meeting the delegation was Dai Qing, a journalist who wrote scathingly about the environmental impacts of the massive Three Gorges Dam. In a telephone interview on Saturday, she described the indignities of having her phone calls monitored, which is how the authorities knew of the invitation, she said.

When she insisted on meeting the Americans for brunch last week, a security official arrived in her living room with a warning that disobedience would lead to even more draconian surveillance — including a carload of police parked outside her Beijing home day and night. “That’s just trouble for everyone,” she said the official told her apologetically.

Since 2008, after the police forced the cancellation of yet another seminar in Beijing, the Independent Chinese PEN Center moved its annual events to Hong Kong. Asked about the logic behind the increased government restrictions, the group’s president, Tienchi Liao, said she thought Beijing was simply trying to show writers it still held all the cards. “They decide when people can write, when they can publish and when they can join literary activities,” said Ms. Liao, who lives in Germany. “For us, this is really, really sad.”