James Miles reports from Beijing:

The Chinese police have reportedly detained a leading dissident involved in attempts to form an opposition political party.

According to the Hong Kong-based Information Centre of Human Rights and Democratic Movement in China, the dissident, Wang Youcai, was taken into custody on Monday.

Mr Wang was a prominent student leader during the Tiananmen Square protests of 1989.

The Hong Kong group said Mr Wang's wife was informed by the police that her husband had violated orders to inform the authorities every time he left his home in the eastern city of Hangzhou.

This order was imposed in August when Mr Wang was unexpectedly allowed to return home after spending more than a month in jail for attempting to form an opposition political party.

China's decision to release Mr Wang instead of pursuing its original charge that he had incited the overthrow of the government was an unusual departure from its normal practice of sending leaders of dissident groups to prison or labour camps.

It is not clear whether Mr Wang's latest detention signals a change of heart by the government or is simply intended as a warning.

Since Mr Wang first attempted to register a local branch of the China Democracy Party in June, numerous other dissidents around the country have tried to do the same.

Several have been briefly detained, but no charges have been pressed.

The Hong Kong human rights group said that two Chinese activists, both based overseas, had also gone missing in Hangzhou this week. The group said the two may have been detained for meeting Mr Wang.