The police have arrested a prominent activist, Hoang Duc Binh, for his role in an environmental campaign, provoking a tense confrontation with citizens.
Mr Binh has been working with Catholic priests in Nghe An province to defend the rights of residents affected by last year’s toxic leak from the Formosa steel plant.
They are demanding compensation, transparency and the closure of the Taiwanese owned plant which caused the death of more than 100 tonnes of fish.
Mr Binh was charged with abusing democratic freedoms under Article 258 of the penal code, often used to silence government critics, and with opposing officers on duty.
State media said he had used discontent over the toxic spill, which devastated the local fishing industry, to stir up unrest.
Reports said that he was travelling in a car with an influential local priest, Nguyen Dinh Thuc, when they were pulled over and he was taken away by plain clothes officers.
An arrest warrant was also issued for another activist, Thai Van Dung, for allegedly violating probation.
News of the arrest sparked an immediate protest by local people in front of the district office in Dien Chau, Nghe An.
Hundreds gathered to demand Binh’s release but they dispersed at the request of priests who were concerned about possible clashes with gathering security forces.
He is the latest in a series of bloggers and activists to be arrested in connection with the environmental protest movement.
Tension is continuing to grow in the central provinces worst affected by last year’s disaster, and the government is stepping up efforts to crush the challenge to its authority.
State media have warned in recent weeks about possible action against the priests who have taken a leading role in the campaign.