BANGKOK — Four democracy advocates in Vietnam were convicted Wednesday in a closely watched trial of trying to overthrow the state, prosecuted as part of campaign against dissent that has led to dozens of arrests in recent months.

The sentences ranged from five years in prison for the most prominent defendant, Le Cong Dinh, 41, an American-educated human rights lawyer, to 16 years for a well-known Internet entrepreneur and blogger, Tran Huynh Duy Thuc, 43.

Another democracy advocate, Nguyen Tien Trung, received a seven-year sentence, while Le Thang Long, who worked with Mr. Thuc, the blogger, was sentenced to five years.

All but Mr. Thuc had been charged with subversion, an unusually severe charge that can carry the death penalty. Foreign analysts said the charge was intended as a warning and an assertion of the limits of political discourse before the nation’s Communist Party congress next year.

Some of the dissidents admitted to pushing for multiparty democracy, which does not exist under Vietnam’s one-party Communist state.

Last month another dissident, Tran Anh Kim, 60, a former army officer, was sentenced to five and a half years in prison, also on the charge of subversion. In October, nine people were sentenced to prison terms of two to six years for hanging banners that called for multiparty democracy.

Foreign governments and human rights groups have spoken out against the continuing crackdown, which has included tighter limits on press freedom and on Internet discussion sites, including political blogs. Access to Facebook has recently been restricted.

During the one-day trial in Ho Chi Minh City, Mr. Dinh agreed that he had broken the law by meeting with foreign groups and by advocating multiparty democracy in Vietnam. His remarks and details of the court proceedings were reported by journalists and foreign diplomats who were permitted to observe the courtroom on closed-circuit television.

“From the bottom of my heart, I myself and these three other defendants had no intention to overthrow the government,” Mr. Dinh said, according to news reports. He added, “During my studies overseas, I was influenced by Western attitudes toward democracy, freedom and human rights.”

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