BEIJING (AP) _ A former Tiananmen Square student leader who tried to form an opposition party has been detained in the eastern city of Hangzhou and two other dissidents are missing, a human rights group said today.

Police took Wang Youcai from his home Monday and then told his family a day later that he had been detained for allegedly leaving home without police permission, the Information Center of Human Rights and Democratic Movement in China reported.

The police did not say how long Wang would be held, the Hong Kong-based group said. Wang was released Aug. 30 after spending seven weeks in detention following his attempt to form a political party to challenge the Communist Party's monopoly on power.

Two other dissidents who had returned to China from overseas exile disappeared Monday in Hangzhou and possibly were also in police custody, the group said.

Wang Ce and Li Li, who had returned from Spain and France respectively, had told colleagues they were returning to China to promote political change, the center said.

Wang Youcai and other activists announced the formation of the China Democracy Party on June 25, the day President Clinton arrived on a visit. After Clinton's departure, police detained Wang and 11 others in connection with the party.

Police have since detained or interrogated many of those connected with the group, and officials have rejected repeated attempts by dissidents to register the group as required by law.

In 1989, after the military quelled democracy demonstrations in Tiananmen Square, Wang was on its list of 21 most-wanted student leaders. He was caught and sentenced to prison, but released early in 1991.