A Chinese man who handed out fliers in local parks about imprisoned Nobel Peace Prize winner Liu Xiaobo has been detained on suspicion of subversion, a rights group and a fellow activist said Wednesday.

It's the first such action taken against a Liu supporter since the Nobel prize announcement last month though many Liu supporters have reported police harassment, the group China Human Rights Defenders said.

The move marks a serious turn for anyone inside China who shows open support for Liu, whom the government calls a criminal for his demands for widespread political reform. It initially blocked news reports of his award and has been waging a campaign through state media to criticize both Liu and the prize.

Guo Xianliang, an engineer from the southern province of Yunnan, disappeared Thursday while on a business trip in the southern city of Guangzhou. He had been handing out fliers on the streets and in public parks there, the China-based rights group said.

Guo writes online about democratic reform but is not a well-known activist, and the group said he has not been in trouble before.

"Most known activists celebrated Liu's peace prize among themselves. The government was already quite sensitive," said research coordinator Wang Songlian. "Guo took it a step further by introducing Liu Xiaobo to the public."

She said Guangzhou authorities are already sensitive to anything they think disturbs public order because the city is preparing to host the Asian Games this month.

The fliers were titled "Liu Xiaobo, a Name to Be Proud of," said Guangzhou-based activist Ye Du, who is a friend of Guo. "They told the public who he was and what he did, and let people know a man who had been fighting for Chinese democracy and who is respected by people all over the world is still in jail."

Liu is serving an 11-year sentence for subversion, a vaguely worded charge that is routinely used to jail dissidents in China.

Ye said the reaction of authorities was ridiculous.

"Liu Xiaobo's winning of the peace prize is a fact, and he was just letting the public know the truth," he said.

Wang said police told Guo's wife on Tuesday that Guo had been criminally detained. The mobile phone of the wife, Yang Di, was turned off Wednesday.

If police follow up by formally arresting Guo on the subversion charge, he would go to trial.

Police in Guangzhou had no immediate comment.

Ye said police came to his home Tuesday to ask whether he helped plan the fliers. He said he did give Guo some suggestions.

Ye said police confiscated his computer.

Separately, pro-democracy lawmakers in Hong Kong took advantage of the southern financial hub's semiautonomous status on Wednesday to honor Liu.

Opposition legislators lined up to pay tribute to the Chinese dissident in a debate triggered by colleague Raymond Wong, who proposed a resolution demanding Beijing release Liu and other jailed dissidents.

Wong's motion, however, is expected to be defeated because Beijing loyalists control the Hong Kong legislature, which is half-elected, half-chosen by interest groups that typically side with the mainland Chinese government.