MANAGUA, NICARAGUA, SEPT. 20 -- The Nicaraguan government has authorized the immediate reopening of the opposition daily La Prensa, free of censorship, in an effort to comply with a Central American peace plan, the paper's directors and the government announced today.

Publisher Violeta Chamorro said she was beginning to call the staff back to work and hopes to have an edition on the streets by Oct. 1. The paper was shut June 26, 1986, following approval of $100 million in U.S. aid to rebels battling leftist rule here. Before that, it had operated under extensive prior censorship.

The decision was the most significant in a series of actions by the Sandinista government to meet the terms of the peace accord signed in Guatemala on Aug. 7 by the five Central American presidents. It calls for, among other points, freedom of expression in all five countries by Nov. 7.

"We now have freedom of the press in our newspaper. This is the peace accords at work," Chamorro said.

Vice President Sergio Ramirez said his government agreed to the move "as a goodwill gesture . . . to help reunite Nicaraguans torn apart by war and conflict."

The government also has named a commission, as required by the peace pact, and headed it with the government's most influential critic, Cardinal Miguel Obando y Bravo, to oversee implementation.

In addition, Managua allowed two Roman Catholic priests to return from exile. Last Sunday, it freed 16 Central Americans captured as mercenaries for the rebels, known as contras.

The contras, for their part, freed 80 prisoners Friday in what was described as a gesture in support of the peace plan. Of those freed in Costa Rica, only 20 returned to Nicaragua, where they received a cool, low-key reception.

So far, only La Prensa will reopen under the terms of a joint government-La Prensa communique that Chamorro read at a news conference. Other nongovernmental media, including the Catholic Radio, remain closed. But Ramirez said the government will discuss returning that radio to the air "in the very near future and with the best possible will."

The Chamorro family, which has run La Prensa for more than 60 years, got permission to reopen after two days of intense negotiations with President Daniel Ortega, in which Costa Rican Foreign Minister Rodrigo Madrigal Nieto acted as a go-between, participants said.

La Prensa's directors struck the final agreement yesterday with Agrarian Reform Minister Jaime Wheelock, acting on behalf of Ortega. While that was occurring in the study of Chamorro's house, family members said, the publisher was meeting in her dining room with a delegation led by Sen. Christopher J. Dodd (D-Conn.).

The Chamorros said they decided purposely not to inform Dodd's delegation, which included Sens. Terry Sanford (D-N.C.) and John S. McCain III (R-Ariz.), about the breakthrough to avoid any American involvement.

According to the communique, the paper will come out "with no other restrictions than those imposed by the responsible exercise of journalism."

Chamorro said the government issued no warnings or conditions, and she added that the editors would not engage in self-censorship. However, La Prensa promised in the communique to promote "a climate of peace."

Carlos Holmann, the paper's chief administrator, said that only after intense discussion did Ortego accede to La Prensa's demand that there be no prior censorship.

Holmann said he was first approached by Wheelock early this month with an offer to open the paper with "moderate censorship," in which Sandinista supervisors would excise news about the war with the contras and about the economy. Holmann said he refused.

Then, after meetings Thursday and Friday between Ortega and Madrigal, who is Costa Rica's top diplomat as well as a family friend of the Chamorros, Ortega paid a surprise hour-long visit yesterday morning to the Chamorro home.

The peace plan is based on a proposal by Costa Rican President Oscar Arias, who is to meet this week in Washington with President Reagan, a recent critic of the peace effort.

Ortega reportedly reiterated the offer for limited censorship, and La Prensa's editors again refused. Ortega left, but Wheelock returned to represent him in a three-hour parley yesterday afternoon.

In addition to agreeing to end censorship of La Prensa, Wheelock also pledged that it would be allowed to buy newsprint from the government, the only supplier in Nicaragua, Chamorro said.

The government also agreed to refrain from harassing La Prensa reporters, the publisher said.

One of Chamorro's sons, Pedro Joaquin Chamorro, a former news editor of the paper, is in exile in Costa Rica and is a leader of the Nicaraguan Resistance, the main contra alliance. He has said he might consider returning to Nicaragua if the paper opened without censorship. But his mother said today that he will return only when there is a general amnesty in Nicaragua under the peace plan.

La Prensa reported a daily circulation of 65,000 when it closed and said it employed about 230 Nicaraguans. The government charged it was a tool of the Reagan administration because the paper accepted a donation of materials from the Washington-based National Endowment for Democracy.

Nicaragua's two other dailies, Barricada and El Nuevo Diario, are government-controlled.