TAIPEI, TAIWAN, FEB. 12 -- Chinese Communist authorities in Beijing today sentenced two democracy activists to 13 years in prison as major figures behind the scene in the Tiananmen Square protests of 1989.

Economist Chen Ziming, 38, and journalist Wang Juntao, 33, were accused of subverting the socialist system. The Beijing court's sentences were the most severe since the current round of prosecutions began late last year.

The pair "committed very serious crimes but have so far shown no willingness to repent," the official New China News Agency said. They were convicted of inciting subversion of the government, organizing illegal groups, and directing "attacks against the armed forces" while under martial law.

Chen has been on a hunger strike since Feb. 7 in an attempt to postpone his trial and Wang reportedly has hepatitis.

Liu Gang, 30, a researcher who worked closely with Chen and who helped organize protesters during the 1989 demonstrations, also was convicted of subversion but received a six-year sentence because "he acknowledged his crimes and showed willingness to repent," the news agency said.

Chen Xiaoping, 29, a constitutional law scholar, was convicted on the same charge but released "for voluntarily giving himself up to police and showing willingness to repent," the news agency said.

Under the Chinese judicial system, which is controlled by the Communist Party, defendants are under enormous pressure to confess, for which they receive leniency, while those who resist are dealt with severely.

Unlike the Chinese student leaders who captured worldwide attention during the democracy movement, these intellectuals, who were acting as the behind-the-scenes advisers, are little known outside China.

The government charged that they "manipulated" the students of the democracy movement to attempt overthrow of the government. But according to a recent report by Asia Watch, a New York-based human rights organization, the intellectuals tried to steer the student demonstrators "toward realistic channels of protest that might minimize the chances of violent confrontation" and tried to persuade the students to evacuate Tiananmen Square in advance of the impending Chinese Army crackdown on June 4, 1989. The government has said 300 people were killed at that time.

In staging the trials of these dissidents, the authorities "may be settling accounts with the entire course of the pro-democracy movement in China since 1976, by punishing the main veterans," Asia Watch said.

As with other recent trials, the official news agency reported that the hearings were public, with local residents in attendance. The news agency did not report what the defendants said. Foreign reporters and diplomats have been barred from attending.

A visibly weakened Chen Ziming rejected as "unfair and incorrect" the charge that he plotted to overthrow the government, according to attending family members who were quoted by Western news agencies. Liu, by these accounts, protested his innocence but Chen Xiaoping told the court he would have liked to overthrow the "corrupt government."

Authorities decided to move ahead with the current round of prosecutions late last year when it became apparent that the domestic political situation had stabilized. Beijing could be taking advantage of international preoccupation with the Persian Gulf War to press ahead with the trials.

Chen Ziming and Wang have been involved in a decade-long effort to revamp the party and government from within through a privately funded network of think tanks that explored the consequences of China's economic changes and outlined the need for parallel political ones.

Premier Li Peng reportedly has labeled Chen and Wang "the black hands behind the black hands."

Both began their careers of dissent during the 1976 outpouring of grief to mourn the death of premier Zhou Enlai, and to protest the repressive policies of the Cultural Revolution. The demonstrations were deemed counterrevolutionary and were violently suppressed. But later, senior leader Deng Xiaoping led the overturning of the official verdict on the incident.

Chen and Wang were active in the Democracy Wall protest posters movement of 1978-1979. In 1985, they set up the Beijing Social and Economic Sciences Research Institute to parallel a prominent government think tank on economic reform.

Left unsettled are the fates of disgraced ex-party chief Zhao Ziyang and two high-level officials within Zhao's inner circle, who have been detained since 1989. Zhao was dismissed as party chief in June 1989 for his alleged role in splitting the party and supporting the democracy movement. His political status is still unclear.

{In Washington, State Department spokesman Margaret Tutwiler said the United States found the sentences "deeply troubling" and questioned the "justice, fairness and due process" of the trials.}