BANGKOK — A well-known Vietnamese dissident has been convicted of speaking out inside prison against the ruling Communist Party and sentenced to another 11 years, in a move rights activists said Tuesday highlights the country’s strict suppression of any opposition.

Trinh Ba Phuong, who was already serving a 10-year sentence on charges of spreading anti-state propaganda, was convicted Friday by the People’s Court of Da Nang for writing “down with the Communist Party of Vietnam for violating human rights, down with the Communist court for wrongfully convicting me” on a piece of paper found in his cell, according to The 88 Project, a group focusing on human rights abuses in Vietnam.

The conviction was reported by opposition media based outside of Vietnam, which said Phuong had denied writing the statement allegedly found in his cell. Vietnamese state-run media did not report the case and Vietnam’s Ministry of Foreign Affairs did not respond to a request for comment.

Elaine Pearson, Asia director for Human Rights Watch, said the conviction showed there was “zero tolerance for dissent in Vietnam” and noted that it came as the European Union’s trade commissioner was in Hanoi meeting with local officials looking to improve ties with Vietnam.

“At this time, while a senior European trade official is on a charm offensive in Hanoi, it is critical that concerned governments also raise concerns with the Vietnamese government about the crackdown on free expression and press for the release of activists like Trinh Ba Phuong detained for peaceful acts of free expression,” she told The Associated Press in an email.

According to a copy of the indictment obtained by The 88 Project, Phuong was accused of “consistently having displayed a defiant and resentful attitude toward the communist regime” under Article 117 of the country’s criminal code.

“Phuong’s case highlights Vietnam’s tight grip on dissent,” the group wrote in a report on the conviction. “Vietnam routinely uses vaguely worded criminal code provisions like Article 117 to silence activists, journalists, and bloggers.”

The 40-year-old is a campaigner in support of human rights, land rights and environmental protections, whose parents were imprisoned in 2014 for participating in protests themselves.

Phuong garnered international attention as an author of a report documenting abuses during a January 2020 raid by police in which an elderly farmer and three officers were killed during a bid to move farmers off their land, according to The 88 Project.

He was arrested later that year and convicted in 2021 of spreading propaganda against the state.

His most recent conviction is “the first instance of a Vietnamese political prisoner being prosecuted for their speech while already imprisoned,” according to The 88 Project.

“From the perspective of international law, Phuong was merely protesting human rights abuses by the Vietnamese government and his alleged wrongful conviction,” the group said.