Police in Vietnam have arrested more political activists in coordinated raids across the country.
A statement from the Ministry of Public Security said that four detainees were being held under Article 79 of the penal code on charges of attempting to overthrow the people’s administration.
The arrests, across the length of the country, mark a further escalation of the government’s drive to suppress dissent.
Reports say that journalists from an independent TV channel, Chan Hung Nuoc Viet, have also been summoned and arrested.
Rights campaigners fear the authorities are going all out to silence their online critics, with recent appeals for restraint from foreign governments falling on deaf ears.
Family members confirmed that the engineer and former political prisoner, Pham Van Troi, was arrested at his home in Hanoi.
Pastor Nguyen Trung Ton, who has also served a prison sentence on political charges in the past, was detained in Hanoi.
The journalist, Truong Minh Duc, was picked up in Ho Chi Minh City. Nguyen Bac Truyen was later arrested in the same city.
The four are accused of associating with the human rights lawyer, Nguyen Van Dai, who was been held without trial since December 2015 along with his assistant Le Thu Ha. The ministry said Dai and Ha were now also being charged under Article 79 after initially being arrested for spreading propaganda against the state under Article 88 of the penal code.
The arrests follow the detention on Monday of the blogger, Le Dinh Luong, who is being held on the same charge.
Harsh prison sentences of nine and ten years imposed on two celebrated female bloggers in recent weeks have shown the renewed determination of the Communist party to silence dissent.
The party leadership is no longer constrained by criticism of its human rights record from the United States, the European Union and other western governments.
One western diplomat involved in human rights dialogue with the Vietnamese government in recent months said that his requests for information had been met with ill-disguised hostility and anger.
The lack of interest in human rights shown by Donald Trump is thought by some observers to have been interpreted as a green light for further repression by the Communist party leadership.
The Hanoi government’s alarm at the extent of public dissent over last year’s environmental disaster off the north-central coast also appears to have fuelled internal arguments for a harsh crackdown.
The prime minister, Nguyen Xuan Phuc, recently visited the scene of the chemical leak at the Formosa steel works in Ha Tinh, in an indication of the high priority still being given to the issue. A number of senior local officials were named as having some responsibility for the disaster in a rare display of contrition, even though the process is limited and lacking in any attempt at transparency.
The government is also highly sensitive to domestic criticism, and free exchanges of information on the internet, at a time of intense pressure from China over territorial disputes in the South China Sea.
Hanoi has not denied foreign reports that it was forced to cancel its latest attempt at drilling for gas in disputed waters because of a direct threat from China of military action.
The Communist authorities know they would be vulnerable to charges of national betrayal should such reports be picked up civil society groups at home.