In a move that appeared to be aimed at the political opposition, and particularly Catholic Church leaders, Nicaragua's ruling Sandinistas have abruptly reinstated and broadened widely criticized restrictions on civil liberties in Nicaragua.

The decision, announced last night by President Daniel Ortega, appeared to close a period during which the Nicaraguan government sought to parry criticism of its rule by relaxing or selectively applying strictures of a state of emergency decreed in March 1982 and renewed every six months as part of the war against U.S.-sponsored insurgents.

Ortega said U.S. backing for rebels fighting to overthrow the Sandinistas made necessary the new steps, which he described as a year-long state of emergency now applied to the entire country. Parts of the previous emergency decree had been suspended except in war zones since summer 1984, when the country prepared for presidential elections that in November endorsed Ortega's leadership by a comfortable margin.

In Washington, administration officials harshly criticized the move, which the State Department described as "a further step toward imposing a totalitarian regime on the people of Nicaragua."

Press censorship, which had been eased but not abolished, was reaffirmed in the new decree, leading to speculation that it would be applied more stringently to the caustic opposition newspaper La Prensa and Roman Catholic Church publications. Interior Ministry censors since the summer of 1984 had been permitting more latitude in criticism of the government as long as it did not touch on the war against U.S.-backed rebels or sensitive economic problems such as shortages.

But the ministry forcefully halted an attempt last week by the Rev. Bismarck Carballo, spokesman for the Nicaraguan church hierarchy, to publish a magazine in defiance of government censorship and other restrictions. The ministry's actions, which included taking over diocesan offices to prevent publication, fit into a pattern of increasing confrontation here that official Nicaraguan sources said led to Ortega's harsh measures.

Under the new or reinstated measures, Nicaraguan workers no longer have the right to form labor unions or go on strike and political groups no longer have the right to hold rallies or demonstrations. In addition, Nicaraguans no longer have the right to move about the country and live where they see fit. The privacy of mail and business accounts is no longer guaranteed. The right to habeas corpus was suspended, as was the right to appeal convictions in court and refuse self-incriminating testimony.

"This is a near-fatal blow to the political process in Nicaragua," said Virgilio Godoy, head of the Independent Liberal Party, United Press International reported. He and other opposition figures suggested that the move may halt the drafting of a new constitution by the National Assembly elected last November.

It remains to be seen how severely Sandinista authorities will apply the new or reinstated restrictions, making the effect on everyday life difficult to gauge. Some rights, such as the right to strike, were already limited by the government even though they existed on paper. In any case, the emergency decree seemed to give the government broad new legal weapons to combat dissidents.

"It goes a lot farther than anything they had before," said a diplomat.

Ortega listed as reasons for his actions renewed U.S. aid for the rebels; faltering peace efforts by the Contadora group of Latin American nations, which he said were sabotaged by the United States; U.S. financial and trade measures against Nicaragua, and support for these U.S. policies by what he called Nicaraguan "agents of imperialism."

These agents, he charged, are working "from some political parties, from some communications media or religious institutions." This seemed to be a reference to the Democratic Coordinator, an opposition alliance, and the Catholic Church hierarchy, which has joined the Reagan administration in calling for dialogue between the government and the rebel leadership.

"There is a group of religious who are trying to act as an internal front within a country at war," said a government official.

Observers noted that Commander Joaquin Cuadra, the Sandinista chief of staff and deputy defense minister, reported at a news conference Monday that government forces have gained the upper hand in recent months against the rebels, based in Honduras and Costa Rica. Against that background, they said, the crisis portrayed by Ortega as the reason for his measures two days later was difficult to understand.

One official Nicaraguan source said the Sandinistas' determined attitude grew from an accumulation of signs that opposition from the Reagan administration and political enemies within was as tough as ever despite the relaxations in civil liberties allowed last year.

One particularly important sign, the source said, was a declaration Oct. 10 by Assistant Secretary of State Elliot Abrams calling for increased pressure on Nicaragua. Another, the official said, was increased Honduran Army presence along the Nicaraguan border.