More than 160 prominent writers, scholars and human rights advocates outside mainland China have signed an open letter to President Hu Jintao asking him to release a well-known intellectual who was detained earlier this month. The letter was posted on the Internet on Tuesday.

The letter to Hu indicates that the case of Liu Xiaobo, the intellectual, is quickly turning into the latest human rights cause célèbre in China and could further embarrass the Communist Party at a time when Chinese leaders are celebrating the 30th anniversary of its policy of"reform and opening up."

Among the writers signing the letter are three Nobel laureates in literature - Nadine Gordimer, Seamus Heaney and Wole Soyinka - as well as other scribes who regularly champion freedom of expression, including Umberto Eco and Salman Rushdie.

Just as notable is the fact that an array of foreign China scholars have signed the petition. Academics specializing in Chinese studies are often cautious about taking stands on political issues deemed sensitive by the Communist Party because the Chinese government has a track record of denying visas to people who publicly oppose the party's views. Some of the scholars who signed the petition are already on the Chinese government's blacklist, while others still have regular access to the country.

The scholars include Geremie Barmé of Australian National University; Richard Baum of the University of California, Los Angeles; and Andrew Nathan of Columbia University.