The US State Department has condemned the jailing of one of Vietnam’s most prominent environmental activists for tax fraud in a ruling human rights activists claimed was a “total sham.”

Hoang Thi Minh Hong, 51, who has led environmental campaigns in the communist country for at least a decade, was sentenced to three years in prison by a court in Ho Chi Minh City on Thursday for evading about $280,000 in taxes, according to her lawyer Nguyen Van Tu.

In a statement, State Department spokesperson Matthew Miller said the United States was “deeply concerned” by her imprisonment and reiterated calls for Vietnam to “release all those unjustly detained” and to “respect the right to freedoms of expression and association.”

“NGO leaders like Hoang Thi Minh Hong play a vital role in tackling global challenges, proposing sustainable solutions in the global fight against the climate crisis, and combating wildlife and timber trafficking,” Miller said.

Vietnam’s opaque legal system has come under increased criticism from Western observers this year, even as the Southeast Asian country draws closer to the United States.

In April during a visit to Hanoi, a delegation of the European Parliament’s Subcommittee of Human Rights expressed “great concern at the worsening human rights situation in the country” calling for the release of “political prisoners” including NGO leaders, journalists and environmental activists, according to Reuters.

The court’s ruling also comes just weeks after US President Joe Biden’s first state visit to Vietnam, in which he elevated diplomatic relations between the two countries – a hugely significant move given Washington’s complicated history with Hanoi.

“Vietnam and the United States are critical partners at what I would argue is a very critical time,” Biden said at the time, referencing climate change. “I’m not saying that to be polite. I’m saying it because I mean it from the bottom of my heart.”

‘Total sham’

Hong was the director of CHANGE, an environmental advocacy group she started in 2013 that “addressed problems of climate change, pollution, and endangered wildlife in Vietnam,” according to Human Rights Watch (HRW).

She was also one of 12 international activists who received a grant in 2018 from the first Obama Foundation Scholars Program at Columbia University, HRW said.

Hong “dedicated herself to educating and organizing young leaders in the effort for a greener world,” according to a bio page on the foundation’s website.

The importance of her cause has been underlined by the United States Agency for International Development (USAID), which lists Vietnam as one of the world’s most vulnerable countries to climate change.

“Typhoons, floods, droughts and landslides frequently threaten a high proportion of the country’s 96 million people and economic assets concentrated along its long, densely populated, coast,” USAID says on its website.

Rights groups said Hong’s trial, which lasted half a day, was the latest example of Vietnam’s government “weaponizing the law for the purpose of political persecution.”

“This verdict is a self inflicted wound on Vietnam’s ability to tackle one of the most seismic issues of our time,” Amnesty International said, adding Hong is the fifth prominent environmentalist to be accused of tax evasion in Vietnam in the past two years.

Ben Swanton, co director of The 88 Project, which advocates for human rights in Vietnam, called her trial “a total sham.”

“This is yet another example of the law being weaponized for the purpose of political persecution,” he said.