Police in Vietnam’s capital on May 21 arrested Hanoi resident and human rights activist Truong Van Dung, charging him under Article 88 of Vietnam’s 1999 Penal Code with “conducting propaganda against the State,” Dung’s wife Nghiem Thi Hop told RFA the same day.

Dung, who was born in 1958, was taken into custody at around 7 a.m. at the couple’s home, Hop said.

“While I was out shopping, I received a phone call from a neighbor telling me he had been arrested, and I came back at 7:30 but they had already taken him away.”

Police in plain clothes then arrived and read out an order to search the house, taking away books, notebooks, laptop computers and protest banners, she added.

Dung had participated in protests in Hanoi including demonstrations against China’s occupation of the Paracel Islands — an island group in the South China Sea also claimed by Vietnam — and protests against the Taiwan-owned Formosa Company for polluting the coastline of four central Vietnamese provinces of Vietnam in 2016.

Public protests even over perceived harm to Vietnam’s interests are considered threats to its political stability and are routinely suppressed by the police.

Dung’s arrest under Article 88 of Vietnam’s Penal Code is the second arrest on national security charges reported since Prime Minister Pham Minh Chinh’s May 12-17 visit to the U.S. Cao Thi Cue, owner of the Peng Lai Temple in southern Vietnam’s Long An province, was arrested on charges of “abusing the rights to freedom and democracy” under Article 331 of the 2015 Penal Code.

Both laws have been criticized by rights groups as tools used to stifle voices of dissent in the one-party communist state.