Police detained and questioned a dissident who wrote an open letter opposing Premier Li Peng's expected appointment as head of China's legislature, a human rights group said Friday.

Police in eastern Zhejiang province interrogated Mao Guoliang for seven hours Thursday before releasing him, the Hong Kong-based Information Center of Human Rights and Democratic Movement in China said.Two days earlier, Mao and six others appealed to the National People's Congress not to allow Li to become congress chairman given his support for the 1989 Tiananmen Square crackdown.

Li declared martial law, clearing the way for troops to move against democracy activists gathered in the square. Hundreds are believed to have died. Many others, including Mao, served time in prison for taking part in protests around the country.

Although the legislature largely approves decisions made by Communist Party leaders, it has become one of China's most pro-gres-sive institutions, drafting laws and meekly trying to assert its constitutional authority to supervise the government.

Its annual session, which this year begins March 5, usually inspires dissidents and others to petition for change.