The Organization of American States, responding to an urgent request from the provisional junta ruling Nicaragua, authorized by acclamation up to $500,000 in food and medical aid for the new government yesterday.

Nicaraguan Foreign Minister Miguel d'Escoto had cabled OAS Secretary General Alejandro Orfila that despite the arrival of considerable emergency aid, there were still "dramatic shortages, especially of food and medicine."

The OAS has taken an unsually active role in seeking to assist the new government after having played a key diplomatic part in the international repudiation of dictator Anastasio Somoza, contributing to his ouster last month.

Shortly after installation of the junta, the OAS sent three experts to "provide all possible cooperation in the urgent task of national reconstruction," as Orfila said then in his initial cable to d'escoto.

In a report yesterday to the OAS Permanent Council, these experts said that 500,000 Nicaraguans were suffering from shortages of food and that the number could easily double with the return of refugees who had fled to neighboring countries.

OAS emergency funds, usually used for relief aid following earthquakes or other natural disasters, currently are depleted but the authorization voted yesterday anticipates replenishment by voluntary contributions from the 28 member nations.

The unanimous action on aid was taken amid applause and statements of support -- including a declaration by the ambassador of Guatemala, who represents a conservative military government known to have strong misgivings about the replacement of Somoza by a leftist guerrilla-dominated junta.

Ambassador Gustavo Santiso Galves recalled the earlier words of the new Nicaraguan representative offering the hand of friendship to the hemisphere.

"We attribute enormous importance to this statement," said Santiso. "The hand of Guatemala is extended in a gesture of friendship to Nicaragua and its government."