Sandinista security officials have tightened censorship during the past two months and, through arrests and interrogations, have issued a series of tough warnings to leading dissidents in political parties, labor unions and the church.

The increased pressure against government opponents has taken place in the framework of stiffened emergency restrictions decreed Oct. 15 by President Daniel Ortega. Measures flowing from that decree have created an atmosphere of heightened determination by the Sandinista leadership to block political opponents from any actions that could assist, even indirectly, U.S.-sponsored rebel forces fighting to overthrow the government.

Lino Hernandez, a lawyer who heads the antigovernment Permanent Human Rights Commission, estimated that more than 300 persons have been summoned for interrogation by the Interior Ministry's General Directorate for State Security since the Oct. 15 order and that about 20 remain in jail. The Rev. Bosco Vivas, auxiliary bishop of Managua, said that total includes "not fewer than 100" Roman Catholic lay activists and 50 priests.

The others have been mainly political party leaders, evangelical ministers and union activists, according to diplomatic sources, Hernandez and interviews with those called in. In addition, U.S. officials have reported that 17 Nicaraguan employes of the U.S. Embassy have been summoned for interrogation, and diplomatic sources said a few Nicaraguan employes of the Honduran and Venezuelan embassies here also have been called in.

Jimmy Hassan, a lawyer and evangelical preacher who heads the Campus Crusade for Christ in Nicaragua, said he was taken away at gunpoint by security police who showed up at his house at 6 a.m. on Oct. 31. After searching his office in his presence, police released him at 2 p.m., Hassan said, but then returned to his home at 11 p.m. with an order for him to report to House 50 in the General Directorate for State Security complex at 8 a.m. the next day.

As Hassan recalled it in an interview, he was accused of being "pro-imperialist" and "a friend of the U.S. embassy" during interrogation by several officers that lasted intermittently until 6:30 p.m., when he was released. Neither Hassan nor a number of other detainees interviewed this week reported physical abuse, although several complained of rough treatment and threats of long prison terms for opposition to the government.

Ortega, in announcing the broadened suspension of civil liberties, said it was necessary to combat an "internal front" working to support the anti-Sandinista guerrillas. Within days, more than 120 persons were arrested in the countryside on charges of carrying messages among rebel units, the government announced. Since then, 50 more have been arrrested on similar charges, according to reports reaching Hernandez's office.

Hernandez said the approximately 300 additional detentions were designed to intimidate political dissidents and encourage them to fall in line with government policies or leave the country.

"I would say the state of emergency was not directed against the armed counterrevolutionaries, but against civic opposition to the government," he said in an interview. "What they are doing is closing the little space that remains."

Luis Rivas Leiva, a leader of the opposition Social Democratic Party who was summoned for interrogation Oct. 20, said the government is tightening up political controls because "they want all the energy on the military front."

"What they have been unable to achieve with mercenary forces, the imperialists try to achieve through their agents," said Deputy Interior Minister Luis Carrion in explaining the expanded restrictions Oct. 20. "They are trying to achieve it through open, cynical and insolent political activity."

Deputy Commander Omar Cabezas, a high-ranking Sandinista security official and author of a popular memoir about his life as a guerrilla, said in explaining the interrogations of a dozen evangelical pastors that their sermons were being used to encourage draft resistance in defiance of the law.

Responding to expressions of concern by related U.S. religious groups, Cabezas asked why such "uproar" should focus on Nicaragua when security forces in countries such as Chile and El Salvador murder dissidents instead of interrogating them and releasing them after a few hours or days as Nicaragua has done.

"This was the great punishment, the great sanction, that we applied to them," he said in a news conference.

"Yes, we have called in Catholic priests and told them they were violating the laws," he added later. "It's the least we can do. They were violating the law. These people not only speak ill of the Patriotic Military Service the draft , but they also invite others to refuse to serve. This is called incitement to crime in Nicaragua, and in any other country."

Bishop Vivas said some lay Catholics summoned for interrogation belonged to committees preparing visits to provincial towns by Cardinal Miguel Obando y Bravo, the country's leading symbol of opposition to Sandinista rule. Since his ascension to cardinal last May, the popular prelate has been making such visits almost weekly.

Although they often took on the air of rallies during the summer, since Oct. 15 the government has forbidden outdoor ceremonies connected with the cardinal's appearances, Vivas said.

Jaime Chamorro, editor of the opposition newspaper La Prensa, said during the same time the amount of censored news has risen from about 40 percent to 60 percent of what his staff tries to report. In addition, he said, the Interior Ministry's Communications and Media Department has launched a new effort to prevent distribution of censored articles, which La Prensa regularly makes available to embassies and foreign correspondents.

The department head, Capt. Nelba Blandon, warned Chamorro in a letter Nov. 27 that such distribution is against the law and that if he continues he risks being held responsible under the Maintenance of Order and Public Security Law. To back up the warning further, Blandon suspended publication of the newspaper for two days this month.