Liao Yiwu, a 52-year-old writer who was jailed for four years after recording himself wailing and reading a poem about the 1989 Tiananmen Square massacre, said he had already boarded his aeroplane in the south-western city of Chengdu on Monday when he was ordered to get off.

“A large group of people were waiting at the entrance,” Mr Liao told the Associated Press from his home, where he said he was now under house arrest following four hours of questioning by security officials about why he wanted to speak in Cologne.

The decision to stop Mr Liao from travelling was greeted with anger by freedom of speech groups, who have accused China of tightening controls over the past two years, despite hopes of that freedoms would be extended after the 2008 Olympic Games.

The PEN American Centre, a group promoting freedom of speech worldwide, said it was “outraged” by the Chinese decision—the 13th time, according to Mr Liao, that he has been prevented from leaving China.

“It is hard to figure what the Chinese government hopes to accomplish by preventing one of its most compelling literary voices from meeting with international colleagues and readers,” said Larry Siems, Director of PEN’s international programmes.

“We call on President Hu Jintao to end all restrictions on Liao Yiwu and all other writers and permit them to exercise their right to freedom of expression, movement, and association as guaranteed by international law.”

However, China’s leaders have taken an increasingly strong line against dissidents this year, handing out a punitive 11-year sentence to Liu Xiaobo, the author of the Charter 08 petition for democracy who has since been nominated for the Nobel Peace Prize.

“Words alone cannot express my outrage,” Liao Yiwu wrote in an email to PEN American Centre. “I’m a writer and never considered myself a political dissident. But Liu Xiaobo was right when he said, ‘To gain and preserve your freedom and dignity, there is no other way except to fight.’”

Guido Westerwelle, the Germany’s foreign minister, issued a statement saying he regretted China’s decision to prevent Mr Liao from travelling to Germany. Mr Westerwelle promised to argue for freedom in an open dialogue with China. “We hope to be able to welcome Liao Yiwu in Germany soon,” he added.

The New York-based Human Rights in China protested against Mr Liao’s latest detention and posted a letter Mr Liao had written to his German readers in the likely event that he was unable to attend.

“I regret to say that I have exhausted all my efforts,” Mr Liao wrote. “In this China, which is free for neither the living nor the dead, my readers, your attentive listening to this story will also comfort me at the edge of the grave,” his letter to German readers said.

Mr Liao, who has been described as one of China’s most distinctive literary voices, became renowned for his poem “Massacre”, based on the 1989 Tiananmen Square killings, which he recorded on tape, “howling and chanting to evoke the spirits of the dead”, according to the Asian Literary Review.

He was imprisoned in 1990 for four years, emerging in 1994 to discover that his wife had left him. He spent several years unable to find a publisher, doing odd jobs which led the encounters that spawned his collection of “Interviews with People from the Bottom Rung of Society”.

Most recently, Mr Liao went to the disaster zone of the Sichuan earthquake to interview survivors who were trying to expose official corruption, an exploit recorded in “Chronicles of the Big Earthquake”, published in Chinese in Hong Kong last year.

Chengdu’s public security bureau had no comment on Mr Liao and referred questions to the foreign affairs office of the city government, which said it was not immediately familiar with the incident.