Vietnam's only independent think tank has disbanded due to a government decree restricting the right to conduct research on the ruling Communist Party.
The decree came into effect on Tuesday and limits political research to certain approved topics.
The think tank, the Institute of Development Studies (IDS), called the government's actions a blow to intellectual freedom.
IDS was an influential body in Vietnam, and frequently questioned the government's views on policy. The organization includes some of Vietnam's leading intellectuals, including economists Le Dang Doanh and Nguyen Quang A, writer Nguyen Ngoc, historian Phan Huy Le, and scientists Phan Dinh Dieu and Chu Hao.
Many of them have served in the government and are members of the ruling Communist Party.
But a new government directive known as Decision 97 prohibits the institute's researchers from discussing their research openly, sharply curtailing its activities.
According to the decree, which was signed by Prime Minister Nguyen Tan Dung, opinions "opposing the line, objectives and policies of the party and state must be sent to the relevant authorities within the party or state and may not be announced publicly".
"We are not happy at all," IDS president and founding member Nguyen Quang A told reporters.
"We are very sad and it took a lot of consideration to make a very hard decision," he said, referring to the organisation's decision to disband.
"As individuals, all 16 of us will carry on the research work, independently of course, and each will have to find a way to speak up," he added.
"Perhaps today, as we are not linked to any organisation and cannot be accused of being part of any organisation, we will make even more critical opinions than before."
According to a Vietnam-based Western scholar, Decision 97 and the demise of IDS signaled that "the appetite for constructive criticism has virtually disappeared" in the run-up to the 11th Communist Party Congress scheduled for early 2011.
He said the arrests, detentions and other steps to put pressure on bloggers, online commentators and newspapers in recent weeks were part of the same effort to silence dissent before the Congress, at which many top leaders will be replaced or reshuffled.
New law closes Vietnam think tank, 15 September 2009,
Vietnam's first private think tank folds, 15 September 2009,
Vietnam think tank disbands to decry restrictions, 15 September 2009,