MEXICO CITY — With a drug war raging around them and an unreliable judicial system in place, Mexico’s human rights activists have their hands full as they grapple with a growing new class of victims: themselves.

“I’m not going to be silenced,” insisted Silvia Vázquez Camacho, an activist from Tijuana, who is now in hiding after receiving a series of threats on her life in recent months. Despite her bold declaration, the fear in her voice was palpable, and she acknowledged that she had been forced to take a respite from her activism.

Mexico has a long history of cases in which the authorities, whether they wear badges or business suits, trample on the rights of the powerless. Acknowledging that, the government 20 years ago created a formal commission to officially identify violations and recommend — but not order — remedies. Citizens groups also rose up, however, to level the playing field and represent victims of wrongful arrests, torture, illegal land grabs and numerous other transgressions.

But the system is being severely tested by what human rights activists say is a concerted attack on their rights. The new reality is that activists now devote a considerable portion of their time helping other activists, who have been threatened or far worse.

“No one is protecting us,” said Juan Carlos Gutiérrez Contreras, director of the Mexican Commission for the Defense and Promotion of Human Rights. “Human rights activists should be able to do their jobs. And we don’t just want protection. We want the government to investigate the threats.”

Amnesty International, in a recent report, outlined 15 cases of threats against Mexican human rights activists in recent years scattered across the country. Although there are no precise tallies, human rights groups say that the number of activists who have been improperly singled out by the police, soldiers and government officials is in the dozens.

In one of numerous new cases on file with Mexican human rights organizations, Ms. Vázquez and another woman, Blanca Mesina Nevarez, recently fled Tijuana because they feared that their lives were in danger as a result of their work. The two activists had been representing 25 police officers who had accused Mexican security forces of torturing them in early 2009 to force them to sign confessions saying that they were taking bribes. The activists suspect that a group of rival Tijuana police officers are the ones threatening them.

The more vocal the activists were in raising the torture allegations, the more intense the response. First there were threatening phone calls. Then police cars began turning up outside their homes and trailing them around the city. After Ms. Mesina testified at a hearing in Washington last fall of the Inter-American Commission on Human Rights, a man in a mask approached her and threatened to kill her.

Alarmed by the intimidation, the Inter-American Commission of Human Rights recently took on the case of the Tijuana activists, calling on the Mexican government to beef up its protection measures for the two women, before it is too late.

For some, like Raúl Lucas Lucía, it already is. Mr. Lucas defended the rights of indigenous people in the state of Guerrero until he was abducted by three men who claimed to be police officers in February 2009. “Keep quiet or we’ll kill your husband,” Mr. Lucas’s wife, Guadalupe Castro Morales, was told in a phone call from someone who reached her on her husband’s cellphone. “This is happening to you because you’re defending Indians.”

Mr. Lucas’s body and that of a colleague, Manuel Ponce Rosas, were found seven days later. The case remains unsolved.

“Do you think you’re so brave?” a man in a car yelled at Obtilia Eugenio Manuel, the founder of an indigenous rights organization, also in Guerrero, in another case compiled by Amnesty International. The man added, “If you don’t go to prison, we’ll kill you.”

She also received three death threats by text message on her cellphone, one of which warned her that no human rights group could save her. Responding to her case and those of other activists in Guerrero, the international human rights commission, which is part of the Organization of American States, called on the Mexican authorities to provide her and dozens of other activists with protection.

In another case, Cristina Auerbach Benavides, who campaigned on behalf of the families of 65 miners who died in a coal mine explosion in 2006, was confronted more than once at her home in Mexico City by men who claimed to be police officers. The incidents occurred when the bodyguard assigned to her by the Mexico City government was off duty.

“Mexico is a dangerous country in which to defend human rights,” said the Amnesty International report, which noted that there were many more cases in the files of the country’s numerous human rights groups.

By Marc Lacey