Mexican authorities are providing police protection to five human rights activists following death threats against them in a letter sent to news media this week. There are some doubts about the letter's authenticity, but police are taking no chances.

The letter sent to several Mexican news organizations demands 30 million pesos, about $3.25 million, to be paid by the Mexican federal government or the five persons named would be executed. But the letter contains no signature or even the name of a group claiming responsibility and does not say how the money is to be delivered.

The appearance of this letter comes less than two weeks after the murder of Digna Ochoa, a prominent human rights attorney, at her office here in Mexico City. Federal District Chief Prosecutor Bernardo Batiz says the city is also providing protection to some people not mentioned in the letter.

He says the reason for this is that the anonymous letter also makes reference to the Digna Ochoa murder, implying that the authors or authors were involved in that killing. As a precaution, the police are increasing their vigilance to protect others who work in the human rights arena.

The anonymous threatening letter, which is full of foul language, also derides the general concepts of democracy and human rights in Mexico. Many Mexican and international human rights observers have questioned the nation's progress in those areas since the murder of Digna Ochoa and pressure on the government to find the killers has intensified.

On Wednesday, the subsecretary of Mexico's Foreign Relations Department's human rights office recognized the need to confront increasing human rights abuses in the country. Mari Claire Acosta said the Ochoa case should lead to a campaign against human rights abuses she said would make clear that "nobody is above the law."

Ms. Acosta is working closely with Mr. Batiz on the investigation of the Ochoa case and the federal prosecutor's organized crime unit is now examining the anonymous letter for fingerprints or any other clue about its origin.