HANOI, Vietnam (AP) — A Vietnamese court on Tuesday sentenced an activist to nine years in prison on charges of producing videos that defamed the country's leadership, in the latest crackdown on dissent.

Tran Thi Nga was convicted of spreading propaganda against the state in the one-day trial at the People's Court in Ha Nam province in northern Vietnam, her lawyer said.

Nga, 40, campaigned against environmental pollution, police brutality and illegal land confiscation, and called for a tougher stance toward China's assertive territorial claims in the South China Sea.

The court also imposed five years of house arrest following her prison term, lawyer Ha Huy Son said.

"I think this is an unjust verdict," Son said. "She did not commit the crime for which she was convicted by the court."

Nga maintained her innocence during the trial, saying she did not oppose anyone, but was only against corruption and injustice, Son said.

Nga's trial in Ha Nam, about 60 kilometers (38 miles) south of Hanoi, came a month after a court in the south-central province of Khanh Hoa sentenced prominent blogger Nguyen Ngoc Nhu Quynh to 10 years in prison on similar charges.

Son said there was no proof that 13 videos used against Nga in the trial — 11 taken from the internet and two allegedly found on her computer — were hers.

The videos were about subjects such as toxic chemicals dumped last year by Formosa Plastics Group's steel complex in central Vietnam in one of the country's worst environmental disasters, Chinese aggression in the South China Sea, and corruption, Son said.

Human Rights Watch has called for her release.

"The Vietnamese government consistently goes to extremes to silence its critics, targeting activists like Tran Thi Nga with bogus charges that carry a long prison sentence, and subjecting their families to harassment and abuse," Phil Robertson, deputy Asia director for Human Rights Watch, said in a statement Monday.

Vietnam opened up to foreign trade and investment three decades ago and has one of the fastest-growing economies in Asia, but the Communist government continues to have almost no tolerance of dissent.

International human rights groups and some Western governments often criticize Vietnam for jailing people for peacefully expressing their views, but Vietnam's government says only law-breakers are punished.