Heavy security flanked the building in southern Ho Chi Minh City as the case began against Nguyen Van Hai, alias Dieu Cay, Phan Thanh Hai and policewoman-turned-dissident Ta Phong Tan, an AFP reporter saw.
The trio face charges of conducting propaganda against the one-party communist state, which are routinely used to prosecute dissidents in a country that rights groups say is conducting a growing crackdown against freedom of expression.
There were no sign of supporters outside the court, after a popular banned blog, Dan Lam Bao (the People Report), claimed they had been prevented from approaching the area by security forces.
The blog ran photographs of people carrying large signs calling for the trio’s release, and reported that at least seven supporters had been arrested early Monday. Police would not comment on any arrests.
Mobile phone signals had apparently been blocked inside the court compound, the AFP reporter said.
The bloggers are to be tried under Article 88 of the Criminal Code, which carries a maximum penalty of 20 years in jail, a lawyer for Dieu Cay told AFP earlier.
In a desperate protest over the detention of her daughter, Tan’s mother committed suicide by setting herself on fire in front of a local authority building in July, causing one of several postponements to the controversial trial.
Tan was arrested last year, while Phan Thanh Hai, who blogs under the name Anhbasg, was arrested in 2010.
Nguyen Van Hai has been in detention since September 2008, when he was jailed for two-and-a-half years for tax fraud.
The trio are all accused of posting political articles on the banned Vietnamese website “Free Journalists Club” as well as writing on their own blogs, denouncing corruption and injustice and criticising Hanoi’s foreign policy.
Communist Vietnam bans private media — all newspapers and television channels are state-run.
In May, Obama said “we must not forget (journalists) like blogger Dieu Cay, whose 2008 arrest coincided with a mass crackdown on citizen journalism in Vietnam”.
Rights groups including Human Rights Watch and Amnesty International have repeatedly called upon the government to drop the charges and release the three bloggers immediately.
Reporters Without Borders ranked Vietnam 172 out of 179 countries in its 2011-2012 press freedom index and identified the authoritarian state as an “Enemy of the Internet” because of systematic use of cyber-censorship.