Sandinistas, like Somoza before them, take aim at Manuaga's only independent daily

''If the Sandinistas close down La Prensa permanantly,'' comments Pedro Joaquin Chamorro Barrios, the paper's editor, ''the ball game is over.

''Nicaragua will have become an authoritarian one-party state - a Marxist one.''

Mr. Chamorro, whose late father ran La Prensa until his assassination four years ago, is not exaggerating the importance of his newspaper. La Prensa has indeed become the symbol of a multiparty, democratic Nicaragua.

Last week's three-day, government-ordered shutdown of La Prensa heightened concern about the paper's future.

This latest incident stemmed from shooting, which injured three Nicaraguans, during a demonstration by government supporters in front of the La Prensa building on the edge of downtown Managua.

Interior Minister Tomas Borge Martinez said after the incident he was closing down the paper ''for a prudent period of time.''

Mr. Chamorro, however, said he is ''convinced this is what they want'' - to close the paper down permanently. Last week, following the incident at the paper, pro-government demonstrators sprayed the front of his home and his car with red paint, lobbed chicken entrails at a wall of his home, and burned a tire two feet from his front door.

Although Nicaraguan government spokesmen disclaim any responsibility for organizing the incident at La Prensa or at the Chamorro home, Mr. Chamorro and other government critics argue that these demonstrators could not go forward without government connivance.

''The real purpose of all this,'' says a source close to Alfonso Robelo Callejas, a Nicaraguan businessman who was a member of the governing junta under the Sandinistas for nine months, ''is to do in the only free newspaper in Nicaragua.''

The government counters that freedom of the press does not include ''license of malign the government'' and accuses La Prensa of doing just that.

Mr. Chamorro, however, argues that its editorial line is one of ''critical support'' for the Sandinista revolution and government. He says that the government actually has ''deviated from the revolutionary process.''

He adds, ''They say we are counterrevolutionary. The demonstration (outside the newspaper office) damages the revolution more than it damages Nicaragua's image abroad.''

The young editor also charges that the Sandinistas are trying to do what the late dictator Anastasio Somoza Debayle also tried to do - shut La Prensa down.

''Isn't it ironic that both Somoza and the Sandinistas are trying to do the same thing?''

La Prensa is the only independent, nongovernment newspaper in Managua. It has a circulation of 75,000 or more daily, nearly twice the combined total of two other newspapers, both of which support the government and both of which are run by members of Mr. Chamorro's family.

But Mr. Chamorro's mother, Violeta Barrios de Chamorro, the widow of the assassinated La Prensa editor, supports her son - and is known to be extremely disturbed about Nicaragua's direction under the Sandinistas.

Like Mr. Robelo, she, too, was a member of the governing junta for nine months, but stepped down, partly for health reasons, partly in protest over the government's trends. And one of these trends is the government attack on La Prensa.

The paper has been forced to suspend publication on six occasions since the Sandinistas took power in July 1979 - four of them this year.

''La Prensa is simply not honest,'' says a government press spokesman. ''It cannot be allowed to go on publishing lies.''

La Prensa was allowed to reappear Jan. 17 with a warning not to ''provoke'' the government.