BEIJING - One of China's most prominent human-rights activists has been arrested after publication of an open letter to the government from hundreds of people seeking an end to one-party rule, according to his wife and a colleague.

The unusually bold appeal was published Tuesday on the Internet, just ahead of yesterday's International Human Rights Day observations.

Police arrested a suspected organizer of the letter, Liu Xiaobo, late Monday at his Beijing home.

His wife told reporters a large group of police officers arrived with an arrest warrant; some took him away, and others stayed to search the house and confiscate computers, books and other belongings.

Another prominent signer of the document, political theorist and activist Zhang Zuhua, also was arrested but was released the next morning after a lengthy interrogation, Zhang said.

According to Zhang, Liu is being detained on suspicion of "inciting subversion of state power."

More than 300 Chinese citizens - government officials, lawyers, journalists, dissidents, artists and rural leaders - signed the petition, called Charter '08, which began circulating Tuesday morning on the Internet.

It calls for change in 19 specific areas, including a new Chinese constitution, an independent judiciary, freedom of assembly, election of public officials, and stronger guarantees for personal freedoms.

"We stand today as the only country among the major nations that remains mired in authoritarian politics," the document reads.

Liu, 53, has been jailed before. A former philosophy professor at Renmin University in Beijing and now the director of the Independent Chinese PEN Center, he spent 20 months in jail for his support of the 1989 student movement at Tiananmen Square.

In 1996, he was sent to a labor camp for three years for criticizing the Chinese Communist Party. Most recently, in early July, he was detained for several days as part of a widespread crackdown on political dissidents before the Beijing Olympics.