LOS TEQUES, Venezuela » When Judge Maria Lourdes Afiuni issued a ruling in December that irked President Hugo Chavez, he did little to contain his outrage. The president, contending on national television that she would have been put before a firing squad in earlier times, sent his secret intelligence police to arrest her.

Then the agents took her to the overcrowded women's prison in this city of slums near Caracas. They put her in a cell near more than 20 inmates whom Afiuni had sentenced on charges like murder and drug smuggling.

“;I've received threats from inmates telling me they will burn me alive because they see me as a symbol of the system that put them in prison,”; said Afiuni, 46, in her prison cell. “;I'm in this hell because I had the temerity to do my job as a judge in a way that didn't please Chavez.”;

Since Afiuni's imprisonment, a dizzying sequence of other high-profile arrests has taken place, pointing to Chavez's recent use of his security and intelligence apparatus to quash challenges to his grip on the country's political institutions. The arrests come at a time of spreading public ire over an economy hobbled by electricity shortages and soaring inflation.

Senior officials in Chavez's government here, including Attorney General Luisa Ortega, say the most recent arrests were necessary to suppress conspiracies or to prosecute people whose comments were deemed offensive to Chavez. In Afiuni's case, Ortega said the judge had illegally freed another high-profile prisoner, the businessman Eligio Cedeno.

In March, intelligence agents arrested Oswaldo Alvarez Paz, a former presidential candidate, charging him with conspiracy after he said in televised remarks that Venezuela had become a haven for drug trafficking; he also supported a Spanish indictment asserting that officials here had helped Basque separatists train on Venezuelan soil.

Only days later, agents arrested Guillermo Zuloaga, the owner of the opposition television network Globovision, after he criticized the government's efforts to shut down media outlets that challenged the president. After an outcry by rights groups, Zuloaga was released on the condition that he could not travel outside the country.

Next, agents arrested Wilmer Azuaje, an opposition lawmaker, on charges of insulting and striking a police official during a heated discussion. Azuaje had in the past revealed corruption claims against Chavez's siblings. Like Zuloaga, Azuaje was released, but the Supreme Court forbade him to discuss his arrest with the media.

The arrests have taken aim at some of Chavez's most prominent critics ahead of legislative elections in September that put control of the National Assembly in play, and they illustrate Chavez's attempts to tighten control over institutions like the judiciary.

Afiuni, previously an obscure jurist, quickly rose to prominence when she freed Cedeno, who had been jailed on charges of circumventing currency controls. The imprisonment of Cedeno, who had previously financed opposition politicians, was explicitly criticized last year by a panel of United Nations legal experts after his pretrial detention exceeded the limits set by Venezuelan law.

Afiuni contended that she was following U.N. guidance when she released Cedeno, who subsequently fled to the United States. But Chavez immediately claimed that she had been bribed to release Cedeno, demanding that she be jailed for 30 years, even if new laws were needed to keep her in prison that long.

“;The corruption charges are false, and prosecutors know that by looking at all of my banking records,”; Afiuni said. “;But the damage to me has been done.”;

Prosecutors overseeing Afiuni's case did not respond to repeated requests for comment. Criticism of her imprisonment from fellow judges in Venezuela has also been relatively muted, a reaction that is not entirely surprising because Chavez and his loyalists in the National Assembly stripped the Supreme Court of its autonomy in 2004.

Outside Venezuela, criticism of her arrest has been more vocal. U.N. legal experts called for her immediate release. The Inter-American Commission on Human Rights said her arrest came within a political system already under stress because of a lack of judicial independence. Independent human rights group have assailed Chavez's government over the arrest.

“;It is not the sort of thing that happens in a functioning democracy, in which judicial institutions offer safeguards for rule of law,”; said Jose Miguel Vivanco, Americas director for Human Rights Watch.

Still, there appear to be relatively few political prisoners in Venezuelan jails, legal experts here say. Twenty to 30 Venezuelans, including Afiuni, are now imprisoned here because of their political activity or for reasons connected to publicly contradicting Chavez's wishes, said Rocio San Miguel, a legal scholar here who leads a nongovernmental group that monitors Venezuelan security.

The high-profile prisoners also include Raul Isaias Baduel, a former defense minister, and Franklin Brito, a biologist arrested at around the same time as Afiuni and put under guard in a military hospital after refusing to end a hunger strike over the government's handling of the seizure of his farmland by squatters.

While Afiuni's case has raised concern over the erosion of judicial independence, the most recent arrests are stoking fears about freedom of expression.

“;The government is fraudulently inventing conspiracies, assassination plots and national emergencies,”; said Alvarez Paz, the former presidential candidate, who was charged with conspiracy after his televised remarks. He is now being detained in a holding cell at the headquarters of the intelligence police. He responded to written questions submitted through his lawyer. “;It is doing so out of nervousness over the precarious decline in the president's credibility at home and abroad,”; he said.

Afiuni said she followed news of the other arrests from a small television in her cell that received a state network signal. She also gets updates from her 17-year-old daughter, who visits twice a week. Otherwise, she remains in her cell and reads, most recently a biography of the Dalai Lama, fearful of venturing into other areas of the prison.

One respite from her life in jail, she said, came when the rehearsal sounds from a prison orchestra of inmates traveled past the bars of her cell. She said its rendition of Vivaldi could move her close to tears. “;Just when I cannot stand it any longer here,”; she said, “;the music lets me escape from reality a little and remember that this nightmare will end someday.”;