The blogger and journalist, Le Anh Hung, is facing years in prison for openly challenging the government’s plans to set up new economic zones.
Hung was arrested on a charge of “abusing democratic freedoms” which carries a jail sentence of up to seven years.
Shortly before his arrest he blogged that police were gathering outside his house and that if he stopped communicating it meant he been “kidnapped”.
Hung had written an open letter to the country’s leaders criticising their plans to open new economic zones that will allow foreign companies to take lengthy leases on land.
He is a member of the Independent Journalists’ Association, which campaigns for press freedom in Vietnam, and is a regular contributor to Voice of America.
The proposal for three new economic zones sparked mass protests in major cities last month and a widespread crackdown by security forces.
The government postponed plans to send the legislation to the National Assembly, stung by claims that Chinese companies would exploit the new zones to extend Beijing’s economic and strategic influence over Vietnam.
“Yet again, Vietnam’s authorities have resorted to the heavy-handed use of repressive laws to shut down peaceful and legitimate criticism,” said Amnesty International in a statement.
“Le Anh Hung was simply using his platform as a well-known blogger to express his opinion about a government policy. For writing a letter he now faces the prospect of up to seven years in jail if convicted.”
Police said that Hung would be held in detention for three months while investigations continued.
The government is acutely sensitive to charges of complicity with China, which many Vietnamese believe poses a growing threat to the country’s sovereignty.
Large numbers of riot police have been deployed in Ho Chi Minh City over recent weekends to prevent a repeat of last month’s mass protests.