Authorities in the southwestern province of Sichuan are holding prominent rights activist Huang Xiaomin under criminal detention for "picking quarrels and stirring up trouble," a charge frequently used to target peaceful critics of the ruling Chinese Communist Party (CCP).

Huang was detained on May 29 by police in his hometown, the provincial capital Chengdu, his friends said.

"I heard from a friend he called using the police phone that he had been detained, and that this time he was looking at a sentence of more than three years in prison," a friend of Huang's who gave only a surname Li told RFA on Wednesday.

"What he did for them to detain him isn't clear yet," Li said. "We don't understand it."

Li said Huang had been writing about vulnerable groups of people fighting for their rights on Mala -- an online forum on Sichuan-related matters.

Huang is a former teacher at a bingtuan CCP party school near Kashgar, in the northwestern Xinjiang Uyghur Autonomous Region (XUAR).

He took part in the student-led pro-democracy movement that ended in the massacre of unarmed civilians by the People's Liberation Army (PLA) on June 4, 1989.

In 2019, the Jinniu District People's Court in Chengdu handed down a two-and-a-half year jail term Huang for supporting a call for direct elections to choose the leader of the CCP.

Huang pleaded guilty to "picking quarrels and stirring up trouble," a charged based on interviews given by Huang to foreign media organizations including RFA, in which he allegedly "attacked the government."

He was earlier sentenced in 2010 by Sichuan's Leshan County People's Court to two years and six months in jail for "gathering a crowd to disrupt social order" for taking part in a street protest outside a court in February 2009.

Another friend of Huang's, Feng Gang, said his most recent detention was likely linked to his advocacy work for disadvantaged groups in Chengdu.

"He helped local human rights defenders and posted details of their cases online, especially to overseas websites, including Twitter and Facebook," Feng told RFA. "He also exposed local corruption and ... criticised the political and legal system."

He received a visit from local police after he gave an interview to RFA in November 2020 about CCP leader Xi Jinping's claim to have eliminated poverty in China.

"Huang has been a thorn in the sides of the local police in Chengdu," Feng said. "He has been detained around the 32nd anniversary of the June 4 crackdown, and ahead of the CCP centenary [on July 1], as part of the local stability maintenance plan."

Huang is also a member of the Independent Chinese PEN Association and one of the conveners of the Sichuan Pan-Blue Alliance, which is politically aligned with Taiwan's opposition Kuomintang (KMT).