An estimated 30,000 Nicaraguans filed past the glass-toped conffin of assassinated newspaper publisher Pedro Joaquin Chamorro yesterday, after 50,000 mourners formed a procession last night that brought the casket eight miles from a hospital to his home in Managua.

Chamorro, 53, the most prominent opponent of dictator Anastasio Somoza, was shot 22 times on Tuesday after his car was cut off by another on the way to work.

Somoza said in a telephone interview with American columnist Nick Thimmesch yesterday that police are holding three suspects, all Nicaraguans.

"I am soory they have assassinated this man Chamorro," Somoza said. "He has attacked my family on a personal level all these years, but he has been consistent." He said it was an isolated incident that should not affect the stability of the Central American nation.

The opposition movement that Chamorro founded, the Decromatic Union for National Liberation, announced, however, that it was breaking off attempts to establish a dialogue with Somoza.

The movement's president, Rafael Cordoba Rivas, said the killing "proves that the authorities have no control of any kind in the country." The now frustated effort at dialogue was pegged to municipal elections scheduled for Feb. 5, which Chamorro's group had vowed to boycott because of alleged rigging.

Reaction to the killing continued, with the State Department denoucing "the despicable act of violence" against "one of the hemisphere's outstanding advocates of human liberty and freedom of expression."

Guido Fernandez, publisher of Costa Rica's La Nacion and chairman of the Inter-American Press Association's press freedom committee, said the death caused "indignation throughout the Western Hemisphere."

In San Juan, Argentina s. Hills, publisher of Puerto Rico's El Mundo newspaper and president of the IAPA, called Chomorro "a hero whose name will be inscribed in journalism's permanent roll of honor." Chamorro was active in the conservative-leaning association of U.S. and Latin American newspaper publishers.

A left-leaning group of 12 exiled Nicaraguans, including Jesuit priest Fernando Cardinal, declared: "As citizens for the rapid establishment of democracy in Nicaragua, we profoundly deplore (Chamorro's) death and are apprehensive that this might mark the beginning of an escalated repression of the oppostion to . . . Somoza."

The interdenominational Washington Office on Latin America circulated the statement by the 12 exiles. The office's director, the Rev. Joseph Eldridge, said, "It appearstaht Dr.Chamorro, like hundreds before him, died as a result of his relentless opposition to the Somoza regime."

Chamorro's body was scheduled to be moved from his suburban home to be viewed first at the headquarters of his politicalmovement and then at the offices of his paper, La Prensa. It was not certain whether the funeral would be Thursday or Friday.

A Nicaraguan Committee of Washington invited all latin Americans as well as Americans in the area to attend a mass for Chamorro on Saturday at 2 p.m. at St. Mathews Cathedral, 1725 Rhode Island Ave.NW.