Last Saturday night in Chengdu (Sichuan) some 20 police officers took Mr Xing from his home along with another activist, Li Yu, who was with him.
Police seized also his computers and papers.
Mr Li was held at a police station for four hours and later taken by force to Deyang City, his home town, where he was released.
Mr Xing was instead detained by police.
Recently he had told foreign media about clashes between Chengdu residents and police.
In the first incident, on 20 February, a resident, Yuan Xinggen had tried to resist an act of forced demolition by throwing kerosene and firecrackers at police, injuring six.
In the second case, about 30 people chained themselves together outside Chengdu Intermediate People’s Court on 23 and 24 February to protest what they believed to be unfair rulings handed down by the court over the years.
Xing, a railway worker, was fired in 2004 for asking that he and his fellow workers be paid for overtime work.
In reaction to that he studied law and began providing legal counsel to help workers defend their rights.
Two weeks ago he set up with others an organisation called ‘Rights Defence in Action’ in Chengdu.
“The arrest is clearly targeted at these human rights defenders, who have tried to exercise their rights to information and expression [and] to report on local rights stories,” CHRD international director Renee Xia said.
“The authorities seem to be desperately trying to ensure ‘stability’ at a time of economic crisis and the approach of sensitive anniversaries, such as the Tibetan Uprising and June 4,” she noted, adding that "stability in Sichuan is particularly essential due to its adjacency to the Tibet Autonomous Region” and to the fact that many areas in the province are ethnically Tibetan.