BANGKOK — A prominent Vietnamese legal scholar who sued the prime minister and called for multiparty democracy was convicted of propaganda against the state Monday and sentenced to seven years in prison and another three years under house arrest. The case was one of the most highly charged political trials in Vietnam in years.

The scholar, Cu Huy Ha Vu, 53, the son of a Communist revolutionary and well-known poet, had drawn unusually vigorous support, much of it spread on the Internet. Catholic churches held prayer vigils over the weekend and a large crowd gathered across the street from the courthouse in Hanoi during the half-day trial.

“I did not commit the crime of spreading propaganda against the state,” Mr. Vu told the court, according to news agency reports. “This criminal case was invented against me. This case is completely illegal.”

Standing in a white shirt and necktie and reading a long verdict, Judge Nguyen Huu Chinh said, “Born and raised into a revolutionary family, he did not sustain that tradition but instead committed erroneous acts.”