One of Vietnam's most prominent dissidents has lost his appeal against imprisonment for tax evasion, as dozens of supporters protested outside the court against the communist state's crackdown on dissent.
Scores of police encircled the Hanoi People's Court of Appeals, which upheld a two and a half year jail sentence for Catholic lawyer and blogger Le Quoc Quan, whose conviction in October was condemned by the United States and denounced by rights campaigners as politically motivated.
"The defendant did not show regret and took a disrespectful attitude towards the court," said court president Nguyen Van Son, confirming the jail term and a fine of around $US57,000 ($A63,280.60).
The television feed to the court's observation room was cut off immediately after the verdict.
Quan earlier told the court he was "completely innocent" of the charges against him.
"I am the victim of a political conspiracy. I object to this trial," said Quan, who was wearing a thick coat and jumper in the courtroom.
Quan - who is on the 17th day of a hunger strike, according to his brother - looked tired and thin as he stood in the dock and appeared to swoon at one point, prompting security guards to prop him up.
His lawyer Bui Quang Nghiem told the court that the tax evasion charges were a joke.
"If you want to try Le Quoc Quan for his activism, you don't need to bring him to court for tax evasion," he said.
The United States said it was deeply concerned by the decision to uphold the conviction, which it called inconsistent with Vietnam's international commitments to freedom of expression.
The 43-year-old lawyer, who blogged on a range of sensitive topics including civil rights, political pluralism and religious freedom, has been in detention since December 2012.
Quan's younger brother, Le Quoc Quyet, said outside the court that the family had not been given permission to attend the hearing.
Shouting "Free Le Quoc Quan" and waving signs calling for the Catholic lawyer's release, around 150 people gathered outside the court as his appeal hearing got underway, causing rush-hour traffic chaos.
The scale of the protest was unusual in Vietnam, where authorities keep a tight lid on dissent.
Hundreds of confused commuters were caught up in the early-morning protest.
