Jin Jiwu, Liu Hai, Li Yingzhi and Song Ge were taken from Jin's home in Xiangtan city in southern China's Hunan province Friday and their whereabouts were unknown, the Information Center of Human Rights and Democratic Movement in China said in a statement.

Police also searched Jin's home and took away his computer and books including contact books, the group said.

Chinese authorities were not immediately available to comment on the report.

The four were detained while discussing plans to press for the release of Zhang Shanguang, a pro-labor dissident who was taken in Wednesday and is now in criminal detention.

Zhang had been trying to form a pressure group for redundant workers and had invited Jin to join, the group said.

The four detained Friday were among 14 Hunan dissidents who met on July 11 to discuss topical political issues, reforms in the political regime and protection for laid-off workers.

The meeting's organizer, Feng Jianru, was picked up on July 14 and held for three days.

Since July 10, Chinese police have detained 21 dissidents and eight of them are still being held.

China had recently charged two other dissidents and sentenced a businessman to three years in jail for helping dissident Wang Xizhe abroad, the group said.

"The series of moves shows that China's human rights situation has regressed instead of improved since Clinton's China visit," the Hong Kong group said.

Clinton's landmark nine-day visit that ended on July 3 had raised hopes among human rights activists that Beijing would reward Washington for closer ties by freeing dissidents.

But just over a week after his departure, the country rounded up activists who had been fighting for democracy and human rights ahead of and during Clinton's trip.

The U.S. has urged the release of Chinese activists held for trying to set up the party during Clinton's visit.

But China has objected to U.S. concern over the detention of the dissidents as interference in its internal affairs, saying most activists were criminals.