Hundreds of Chinese scholars, students and journalists have signed a petition calling for a leftist intellectual to be released from police custody in a case that shows how Beijing's crackdown on civil society extends across the political spectrum.
Zhang Yunfan, a recent graduate of China's prestigious Peking University, was detained last month in the southern city of Guangzhou for "organizing mass gatherings that disturbed social order", the petition says.
News of the detention comes as China cracks down on all forms of "subversion", imprisoning hundreds of activists and lawyers, typically for "rightist" behavior such as promoting human rights or democracy.
But China's leftist intellectuals have enjoyed relatively more space to express views that are out of step with government orthodoxy -- authorities have typically been cautious about attempting to silence them for fear of creating a backlash in the Communist country.
Zhang was helming a group discussion at a local university on authorities' response to leftist speech when local police arrived and hauled away some of the participants, the petition said.
By 5pm Tuesday (0900 GMT) the petition had collected more than 350 signatures.
The unnamed organizers of the petition said they had sent it to the local public security bureau in Guangzhou's Panyu district which is overseeing the case.
Police in Panyu told AFP they could not discuss the case.
Two professors from two of China's elite universities confirmed to AFP that they had signed the letter.
"If he's been arrested for simply participating in a study session that's not right," said Tsinghua University professor Kuang Xinnian.
China's outspoken leftists believe the country's political and economic reforms have abandoned Mao's goal of transforming the nation into a Communist utopia -- citing the growing gap between the rich and poor.
The party's official verdict on Mao -- made public in 1981 -- declared his rule 70 percent good and 30 percent bad, but he is still widely praised for his role as the founder of today's Communist China.