Twenty-four women and two men, whose relatives allegedly disappeared after being arrested by Chilean security police, occupied a United Nations office here yesterday and demanded an international ivestigation of the plight of missing persons in Chile.

The action, described by participants as a hunger strike, is the first public protest by Chileans inside the country over alleged violations of human rights by the military governments."

It was timed to coincide with the opening of the general assembly of the Organization of American States in Grenada and follows a spate of unprecedented publicity in the Chilean press of ongoing security police activity during May.

The denunciations by rights advocates were countered by a government spokesman who charged that they were "organized . . . by groups of persons . . . who seek the condemnation of our country in the OAS."

A spokesman for the hunger strikers said the action was organized to call attention to the cases of 500 missing persons, some of whom disappeared after the military coup in 1973. Their families have undertaken a series of joint legal petitions for court investigations during the past two years.

A statement by the strikers said that the missing persons had all been arrested by security police, "particularly the National Intelligence Directorate, "DINA, and that government authorities, "had either denied the arrests or given contradictory explanations."

The group called for the creation of an investigative commission composed of Chileans and personsof other nationalities who are of "unimpeachable moral qualities."

Lists of more than a thousand missing Chileans have been compiled by international human-rights organizations, the spokesman said, but the list of 500 includes only those whose families are actively pursuing legal efforts inside Chile and have formed an organization called Family Members of Disappeared Detainees.

In recent weeks, Chile's normally muzzled press has raised questions about a series of disappearances that, because of the bizarre circumstances, also appear to be attempts at influencing the debate in Grenada.

The pro-government weekly news magazine Ercilla listed 11 persons who allegedly disappeared or were arrested in May.

The families turned to the Catholic Vicariate of Sodidarity human-rights agency for aid in filing writs of habeas corpus, saying they feared arrests by the secret police. Then two of the missing persons turned up, telling government newspapers they had never been under arrest.

The government newspaper El Cronista charged that the alleged disappearances were staged by the Vicariate on the eve of an "international meeting on human rights," and apparent reference to the OAS meeting.

[The New York-based Council on Hemispheric Affairs charged that Chile staged the disappearances in an attempt to impugn the Vicariate, which has supplied information to the OAS human-rights commission for its reports to the General Assembly in Grenada].

Another disappearance turned out to be a much-disputed kidnapping of the 16-year-old son of a labor leader. (Another labor leader and three other men were arrested by the DINA and charged with the brief kidnaping.

However, Ercilla took the rare step of questioning the official explanation, citing evidence provided by the accused men's employers that they "could not have been at the place of the kidnapping" when it occured.