DANANG, Vietnam (AP) — A court in central Vietnam has sentenced a high school chemistry teacher to six years in prison after he criticized the government.

Judge Nguyen Van Uy says Dinh Dang Dinh was sentenced in a half-day trial Thursday on charges of conducting propaganda against the state.

The official Vietnam News Agency reported Friday that police in central Dak Nong province arrested Dinh last October, confiscating his computer and documents calling for multi-party democracy.

U.S.-based Human Rights Watch said Thursday that Dinh is a former army officer who wrote online commentaries alleging police harassment and signed a petition opposing a planned Chinese-led bauxite mine in Vietnam's restive central highlands.

Vietnam is a one-party state that does not tolerate challenges to its authority. Dissidents frequently receive long prison terms for speaking out.