The neighborhood defense committees that helped the guerrillas win the civil war against former president Anastasio Somoza are playing a major role in what has been a far more orderly transition to peaceful rule than the Sandinistas had expected.

Thousands of defense committee members who were tearing down barricades and burying the dead as the war ended in July are helping to organize the peace -- and raising concern among some non-Sandinistas in the process.

In effect, they have become grassroots appendages of the Sandinista- led government, especially in Managua, with their role including political education, mass organization, surveillance of potential troublemakers and rudimentary military training at the neighborhood level.

On Aug. 11, only three weeks after the Sandinistas took power, Maj. Victor Tirado Lopez told a cheering crowd of thousands in Matagalpa that Sandinista defense committees, organized street by street and block by block throughout Nicaragua, would serve as "the eyes and ears of the revolution."

In addition to their initial duties, Tirado said the defense committees would serve as the base organizations for generating popular support for the programs of the Sandinistas.

The speech was given broad coverage in Barricada, the Sandinistas' official newspaper, because Tirado is one of nine Sandinista national directors. It sent shivers through the upper classes and deeply troubled some diplomatic observers who thought the defense committees' role, as Tirado described it, sounded suspiciously like the beginning of the block-committee surveillance structure used by Fidel Castro to consolidate the Cuban revolution.

In a recent interview, Alfonso Robelo, a non-Sandinista member of the ruling junta, described the defense committees as "civic organizations organized as cells. They are good vehicles for carrying out government programs. But they should not have a police or surveillance role as such."

Yet, in an operating manual distributed to the defense committees, they are told specifically to organize surveillance subgroups to watch out for and report "enemies of the revolution."

Under a section called "surveillance and security," the manual instructs defense committee leaders to form these subcommittees because "each of us must . . . observe suspicious elements in the neighborhoods, find out where they hide arms, where elements of the Somoza militia meet and, above all, communicate this (preferably in writing) to the neighborhood command."

What worries Robelo and other Nicaraguans who hope that, after a transition period, their country will become a Western-style democracy, is not the committees' current vigilance against remaining backers of Somoza, who occasionally still attack Sandinista patrols.

"It is their potential that worries us," said a business leader. "The structure is there for identifying and watching anyone who disagrees with the (Sandinista) front, even if that person played a prominent role in fighting against Somoza."

So far, as defined both in the manual and in practice, enemies of the revolution include only former members of the National Guard who have not been investigated and cleared, informants of the Guard during the war and other supporters of the old government who might try to organize a counterrevolution.

The defense committees also have a political role, which is outlined in the manual and which is being vigorously undertaken in neighborhoods such as the Barrio Rene Schick, one of the most impoverished areas in Managua.

A cadre of young Sandinista veterans, led by Franco Rodriguez Lopez, 22, holds political education classes not only for adults but children as young as 6 years old. About 35 of these youngsters spend two hours each at a little wooden hut called the Rene Schick Sandinista Youth House, where Rodriguez and his assistants teach them about corruption during the Somoza years, the goals of the revolution, Sandinista songs and even military discipline.

Little boys can be seen marching along the dirt streets, their toy guns at the ready. Asked why it was necessary to instill this kind of military feeling in children, Rodriguez at first said the youngsters asked for this type of training.

He added, under questioning, that it was necessary to given even the smallest youngsters military training to defend the neighborhood against whatever counterrevolution might occur.

Wilfredo Canales Argenal, 22, who is second in command of the police post in the Rene Schick neighborhood and who lost his right arm during the war, said he would consider a counterrevolution any future attempt by the "bourgeoisie" to implant a Swedish-style social democracy in Nicaragua.

"We are in the first phase of the revolution now, a phase which is necessary," Canales said. "But our goal is true socialism," which he defined as similar to the systems in Cuba and the Soviet Union.

Canales is not a high government official. But he is a Sandinista veteran who was trained and is active in the most radical branch of the Sandinista movement, which forms a third of the current nine-member directorate of the organization.

The Rene Schick defense committees do more than train children and give classes in political theory. They are responsible for distribution of food and medicament aid, they direct classes for illiterates, organize cultural and sports events and they are trying to secure permission for a neighborhood park.

The nine defense committees that compose the Rene Schick neighborhood grouping seem to have become the center of community life, rivaling even the small Catholic church at the barrio's center. Discussions with a number of residents indicated wide respect and admiration for their work.

Rosario Santamaria, a secretary, said she was aware of charges being made against the defense committee structure.

"All of this talk about communism is part of a counterrevolutionary campaign," she said. "In just a few weeks, we have seen more progress under our new government than we saw during 45 years under the Somoza dictatorship."

Asked if she was not afraid that the defense committees might one day be used to impose a totalitarian system in Nicaragua, she replied without hesitation: "I am more afraid of Tacho's (Samoza's) return."