Anatoly Marchenko, a Soviet dissident who had monitored human rights violations in his country, died Dec. 8, 1986, in Chistopol prison where he had been mistreated.

One year and one day later, Rene Joaquin Cardenas Vargas, director of the Salvadoran government's human rights commission in the provincial town of San Miguel, was shot in the back of the head by three men who had followed him to his home.

Marchenko and Cardenas were two of 10 men monitoring human rights abuses in their countries who were killed in the past 12 months, according to the New York-based group Human Rights Watch. Two others have disappeared and are presumed dead.

The organization released a report yesterday listing reprisals against human rights monitors in 39 countries between December of 1986 and this month. It listed about 500 cases of imprisonment, torture, physical attacks and various types of harassment.

Human Rights Watch said it intends to issue a similar report every year because the work of human rights monitors, "disseminating information about abuses of human rights is the most effective way to curb those abuses."

The countries with the largest numbers of abuses reported are Chile, the Soviet Union, South Africa and Czechoslovakia, where human rights groups are active. But the report pointed out that some nations, such as Saudi Arabia and North Korea, "are so repressive that, as far as we know, no one is able to engage in human rights monitoring."

Many kinds of human rights groups have spread throughout the world since the early 1970s. Some are connected with churches, some are funded by governments or opposition forces, while others are scrupulously neutral. Some groups have formal organizational structures and adequate budgets while others are informal and sometimes clandestine. Most describe their mandate as monitoring compliance with the United Nations' Universal Declaration of Human Rights.

Human Rights Watch is made up of three organizations -- Helsinki Watch, Asia Watch and Americas Watch. The first was founded almost 10 years ago, after Moscow imprisoned organizers, including Marchenko, of a group monitoring compliance with the Helsinki accords on cooperation and security in Europe.