Cu Huy Ha Vu's books come with pages torn out by prison guards. Only some of his letters reach home. He is not allowed to access evidence from his trial or to see his wife alone.

This treatment, described by Vu's wife, has driven the Vietnamese legal scholar to a hunger strike that is now in its fourth week. Nguyen Thi Duong Ha says her husband told her Saturday that he hasn't eaten since May 27, even though she brings him orange juice and chicken stock, and that he won't until the prison officially replies to his complaints.

Now she worries the hunger strike may exacerbate Vu's longstanding heart problems and provoke a stroke.

"I live in fear," she said. "I can't fall asleep because I'm afraid there may be a phone call with bad news."

Vu, the son of revolutionary poet Cu Huy Can, is among the many government critics who have been imprisoned as the Communist government, beset by economic troubles and complaints about corruption and inequality, cracks down on dissent. His hunger strike has drawn attention to the conditions they face in prison and to his own 2011 conviction on charges that included conducting propaganda against the state, calling for multiparty government and demanding the abolishment of the party's leadership.

On Tuesday the U.S. Embassy and the London-based rights group Amnesty International both called for Vu's immediate release. Bloggers have rallied to his cause on the Internet, where Vietnamese continue to express dissent despite the arrests of three prominent bloggers in the past month.

"More and more, we are hearing about harsh treatment of prisoners of conscience in detention (in Vietnam), including solitary confinement, being moved from prison to prison without their families being informed, and inadequate food and health care," said Rupert Abbott, Amnesty International's researcher on Cambodia, Laos and Vietnam.

Vu, a 55-year-old, Sorbonne-educated lawyer, is among the ruling Communist Party's highest-profile critics. His father was not only a famous poet but the agriculture minister in the government of Vietnam's founding president, Ho Chi Minh.

Vu was arrested in 2010 after attempting to sue Prime Minister Nguyen Tan Dung twice _ first for approving a Chinese-built bauxite mining project in Vietnam's central highlands, and later for prohibiting the filing of class-action lawsuits. The first suit was rejected by a Hanoi court, and the second was ignored.

In his dramatic one-day trial in April 2011, Vu's lawyers walked out of the courthouse after a judge refused to read or distribute interviews Vu was accused of giving to foreign media, including the U.S. government-funded Voice of America and Radio Free Asia. He was sentenced to seven years in prison and three of house arrest.

Carl Thayer, a Vietnam expert at the University of New South Wales in Australia, said Vu's case "is an illustration of the counterproductive policies of the Vietnamese Communist regime that seek to intimidate and silence critics." He added that Vu's revolutionary background "only serves to undermine" the regime's legitimacy.

Ha said her husband went on a hunger strike because prison officials haven't responded to the official complaints he has issued in recent months. Vietnamese law requires the prison to respond to petitions within 90 days.

"He wants to be treated in accordance with the law," Ha said in a Hanoi restaurant Monday. "He's a lawyer and he knows that he hasn't done anything wrong."

Vu and his lawyers have complained officially that prison guards have prevented him from accessing evidence from his trial and from meeting privately with his wife when she visits the prison in northern Thanh Hoa province. He also wrote that a prison guard has tormented him by repeatedly opening his door.

Hu said some aspects of prison life have improved for her husband. His 20-square meter (215-square-foot) cell, which at first had no windows and just a rudimentary toilet, has been upgraded considerably in recent months.

Vietnam's state-run media has attempted to raise doubts that Vu is truly on a hunger strike through several recent newspaper and television reports. A doctor at the prison, for example, was quoted by People's Police newspaper Sunday as saying that Vu's health condition was normal.

Deputy prison chief Le Duy Sau told the online newspaper VnExpress that Vu's complaint about the guard opening his door was "completely paranoid," and that Vu would be allowed to see his wife privately _ if he repents for his crimes.

Sau added that Vu receives food from his family, but did not say whether he eats it. Prison officials could not be reached Tuesday, and the foreign ministry did not respond to a written request for comment.

Nguyen Thi Huong, who is engaged to another jailed dissident, said Vietnam's security forces intimidate dissidents' families through a variety of subtle tactics _ including creating administrative barriers that prevent relatives from holding down jobs and attending college, and harassing them for speaking with the media.

Huong's fiance, Nguyen Tien Trung, was jailed in 2010 on charges of plotting to overthrow the government after he advocated for political pluralism.

"They use the whole state apparatus in order to put pressure on the family of those political prisoners and make their lives difficult," Huong said Tuesday from Bloomington, Indiana, where she is completing a doctorate in law and democracy at Indiana University. "It's a very inhumane way for the government to silence dissent."

Ha, who like her husband is a lawyer, is running the family law firm from their French colonial villa in central Hanoi, down the block from the mausoleum where Ho Chi Minh's preserved corpse is displayed. The paint on the villa is peeling, and in the courtyard there is a bust of Vu's father.

Ha said some clients have shied away from their firm because of political sensitivities around her husband's imprisonment, and that the government has prevented the family from opening a Hanoi cafe by rejecting their application for a business license.

When she visited Vu in prison on Saturday, he looked weakened and stressed, she said. She urged him to end his strike, arguing that staying alive is more important than standing by his principles.

But Vu replied that he plans to hang in a bit longer in an effort to force prison officials to respond to his complaints. He also has said he plans to continue advocating for democracy, human rights and Vietnam's territorial sovereignty when he is released from prison.

"He's proud to follow in his father's footsteps," Ha said.