Authorities in the Chinese capital have closed down a non-government think-tank amid an ongoing clampdown on rights activists, rights groups said.
Dozens of municipal civil affairs bureau officials and police searched the offices of the Transition Institute on Social Economic Research in Beijing, confiscating its publications and issuing it with an abolition order, the institute's director Guo Yusan said in an interview.
"About 20 people showed up from the civil affairs bureau and shut down the institute," Guo said. "The reason is that we allegedly didn't register."
"But in fact, we did set up as a company."
Guo said officials had confiscated more than 600 copies of institute publications.
He said the move had come with no official warning: "This was a sudden attack," he said.
The Institute is closely allied to the now-banned Gongmeng public interest and civil rights group, which has provided legal support to activists campaigning for political representation, land rights, migrant rights and other reforms.
The Institute was also a vocal supporter of blind Shandong activist Chen Guangcheng before his escape from nearly two years of house arrest in April 2012.
The banning of the institute comes soon after the detention of leading anti-graft campaigner Xu Zhiyong on charges of disrupting public order.
Rights groups see the moves as part of a widening crackdown on activists who have called on government leaders to declare their assets, and on lawyers who defend "sensitive" cases.
Xu's lawyer Liu Weiguo said the authorities had refused to let him meet with Xu when he tried to visit him at the Beijing No. 3 Detention Center on Thursday.
"The detention center deliberately obstructed me, at first by saying that [Xu] had only just arrived," Liu said. "Then they pretended to make a phone call and told me that Xu Zhiyong had been taken away by police for interrogation."
"I didn't see any police filling out forms there, so I told them I thought they were lying."
A small crowd of Xu's supporters gathered outside the detention center on Thursday, he added.
A second rights lawyer, Chen Jiangang, said he had also been denied permission to see activists Wang Yonghong and Zhang Baocheng at the same detention center where they were being held after campaigning for top officials to reveal their assets, and those of their families.
Shortly after he gave the interview to RFA, Liu himself was detained by police, CHRD reported.
President Xi Jinping has warned that the ruling Chinese Communist Party must beat graft or lose power, sparking a nationwide clampdown on corruption.
However, political analysts say that officials with friends in the right places are unlikely to be touched by the crackdown, and reports suggest many are liquidating their assets and making moves overseas.
Meanwhile, police continue to detain activists who call for greater transparency.
According to an estimate by the China Human Rights Defenders (CHRD) group, 14 activists associated with the anti-graft movement have been formally arrested or criminally detained in Beijing, the central province of Hubei and the eastern province of Jiangxi, on charges ranging from subversion to public order offenses.
Reported by Qiao Long for RFA's Mandarin Service, and by Ho Shan for the Cantonese Service. Translated and written in English by Luisetta Mudie.