Political tension in Hanoi is rising as an intense struggle for the leadership of the Communist Party approaches its climax.
Bloggers and other activists have been called in for long questioning sessions by police, who seem determined to prevent any show of dissent.
Just a week before the 12th National Congress is due to convene to put the seal on new leaders for party and state, observers see signs that party bosses remain locked in dispute over the succession.
The two-term prime minister, Nguyen Tan Dung, has long been seen as the favourite to emerge as the new general-secretary of the Communist Party.
However, his conservative rival, the current general-secretary, Nguyen Phu Trong, appears to have rallied his supporters in a final attempt to block the transition.
“The police are very worried and tense and they seem determined to stop a musical performance being organised by Green Hanoi (environmental activist group). Activists are being forced to hide out because it’s so tense,” said one well known blogger.
The political contest is being played out at a meeting of the Central Committee this week, with signs that the politburo faces a direct challenge from lower ranking party members in the prime minister’s camp.
One widely quote leak said the politburo had proposed that Mr Trong’s term be extended by a year – in the hope that a conservative successor can be groomed to challenge the ambitious prime minister.
Although unable to campaign openly in Vietnam’s opaque political system, Nguyen Tan Dung presents himself as the reform candidate.
He is portrayed as pro-market economy, an enthusiastic backer of the Trans-Pacific Partnership and a promoter of the concessions made to the United States on free trade unions and other labour rights.
“To his supporters, the prime minister is Vietnam’s most proficient statesman, a true reform champion, and patriot ready to end Vietnam’s subservience to China,” says Vietnam analyst Jonathan London of the City University of Hong Kong.
“The prime minister projects a commitment to market liberalising reforms and a willingness to expand freedoms in accordance with the law,” he says.
However, Mr Dung has also been tainted by widespread allegations of corruption amongst his family and cronies, and by the spectacular failure of some of his more ambitious economic schemes.
Bloggers have reported a leaked document in recent weeks said to contain Mr Dung’s own rebuttal of the damaging charges against him.
He is also said to have infuriated conservatives in the leadership with his apparent support for concessions to the United States on human rights – moves that conservatives fear could undermine the party’s monopoly on power.
Mr Dung is also accused of exploiting anti-China sentiment in the party, and society at large, to further his political ambitions.
Nguyen Phu Trong may be seen by many as a stolid and less than inspiring party leader, but he has emerged as the key figure around whom conservatives can rally.
“Party conservatives and in particular the party secretary, Nguyen Phu Trong, retain control over key levers of procedural power and are using these to block the prime minister’s path to power,” says Jonathan London.
Many analysts, however, remain confident that despite the setbacks, Mr Dung will eventually emerge victorious. Once the decision is made, appointments will also be made for the top state posts of prime minister, president and chairman of the National Assembly.
The change may not have an immediate or dramatic impact on policy. Vietnam’s moves to open the economy further and improve ties with Washington – at the expense of China – appear well set.
Observers do believe, however, that the context of the leadership tussle could have long lasting significance.
With 30 million Vietnamese now using Facebook, many ordinary people have for the first time been exposed to active commentary and debate on the political process.
What once seemed dull, bureaucratic and far removed from everyday experience suddenly appears vividly relevant to a country in rapid transition, and a population that feels menaced by Chinese aggression and vulnerable to the vagaries of rapid economic development.