El Salvador's popularly elected president has yet to make the substantial changes necessary to end abuses by police and paramilitary forces, the Organization of American States' human rights commission said yesterday. It also detailed massive violations in Chile, Guatemala and Haiti.

In its 147-page annual report, the Inter-American Commission on Human Rights offered an unprecedented analysis of the political processes occurring in eight countries that have occupied most of its attention in recent years.

The seven-member commission is celebrating its 25th anniversary. In the past it tended to focus on specific violations, particularly of the rights to life and due process, without making judgments on the nature of the government in question.

While welcoming promises by Salvadoran President Jose Napoleon Duarte to implement previous recommendations, the commmission noted that it continues to receive complaints, "although on a lesser scale, of death squad activities, assassinations, kidnapings and disappearances, indiscriminate bombing of the civilian population in zones of conflict with guerrillas and illegal detentions."

Noting Duarte's dissolution of a unit of the Treasury Police notorious for rights violations, the commission observed that the officers involved "have in no way whatsoever been placed under investigation."

Salvadoran institutions dedicated to protecting human rights still find it necessary to operate from Costa Rica or Mexico, said the report, and the Foreign Ministry has refused to cooperate with the OAS commission in its effort to assess any complaints involving the armed forces. OAS members, including El Salvador, are required to offer that cooperation.

In Chile, said the report, the past year has seen "a clear deterioration of the situation of human rights, aggravated by the increasing polarization" of the country in its 12th year of military rule.

Since September 1983, it found, "37 Chileans were killed in repression of demonstrations" and 39 died as a result of "abuses of power" by security forces or in alleged confrontations with them. Some of the latter appear to have been "summary executions," said the commission. It found that 647 persons were wounded by gunfire during protests, while there has been virtually no use of firearms by protesters.

The rights commission attributed the increase in street demonstrations to the cutoff of other means of protest, although it noted "a precarious but real amplification" of freedom of expression during the period.

In Guatemala, the commission found that "the reappearance of death squads" coincided with the coming to power of Gen. Oscar Mejia Victores in a coup. It counted 635 cases of disappearances in the eight months ending last August.

The report welcomed the election of a constituent assembly "in an atmosphere of ample liberty" but lamented continued assaults on personnel of San Carlos University. It named 14 persons killed or missing there since August 1983. The commission also reported that it had found no improvement of the human rights situation in Haiti and Paraguay.

Nicaragua, another country that has occupied the attention of the commission in recent years, was accused of impeding the travel of a citizen who sought to testify before it concerning the imprisonment of his son. The commission reiterated findings of unfairness in the judgments of the Anti-Somocista People's Tribunals, which prosecute members of the government of Anastasio Somoza that the ruling Sandinistas overthrew.

The report included accounts of two turnabouts in respect for human rights: Argentina and Uruguay. The commission praised actions of the new civilian government in Buenos Aires. It criticized the detention by Uruguay of would-be presidential candidate Wilson Ferreira Aldunate but found that "the situation has improved considerably in recent months, especially since an accord between some political parties and the armed forces" that is to lead to elections.