BY ALFONSO CHARDY

  Three men who hijacked a passenger ferry and attempted to steer it to Florida last week were executed by firing squad at dawn Friday after summary trials, infuriating the U.S. government, international human rights organizations and Cuban Americans in Miami.

  The men were charged with ''very grave acts of terrorism'' and sentenced at trials Tuesday, according to an official statement read on Cuban state television. The men appealed -- but the sentences were swiftly upheld by Cuba's Supreme Tribunal and ruling Council of State and carried out shortly thereafter, the statement said.

  No one was hurt in the hijacking, ultimately foiled by the Cuban authorities, for which the three men were executed.

  The three were identified as Lorenzo Enrique Copello Castillo, Bárbaro Leodán Sevilla García and Jorge Luis Martínez Isaac. In Miami, Yordani Montoya, 27, half sister of Martínez Isaac, blasted the Castro regime.

  ''This was an injustice,'' she said. `No one was killed or injured in the hijacking. If he had gotten a prison term, that would have been OK. . . . From Fidel Castro, you can expect anything.''

  In Havana, police reportedly were sent to cordon off the neighborhood where Sevilla García's mother lives, after witnesses said some neighbors went into the streets crying and shouting against the government.

  Though more than a dozen people have been executed in Cuba since 1994, Friday's executions were the first of Cubans charged with terrorism-related offenses in more than a decade. An exile from Miami, Eduardo Díaz Betancourt, was executed in January 1992 after being found guilty of terrorism, sabotage and enemy propaganda following his arrest while on a mission to infiltrate Cuba.

  ''These were almost certainly cases in which the defendants were not given due process and, given that Cuba hadn't carried out death sentences in two years, a
  highlydisturbing development,'' read a statement issued by the U.S. branch of Amnesty International.

  Friday's executions came as a shock, but seemed part of a deliberate hardening of Cuban government attitudes against any act of political dissent. They were the capstone to weeks of heightened political tension on the island, highlighted by scores of arrests of dissidents, stiff sentences against some of those opponents and a string of successful and attempted hijackings.

  Seventy-five dissidents were sentenced this week to terms ranging from six to 28 years on charges of receiving money from, and collaborating with, U.S. officials to
  undermine the Cuban government.

  Senior Cuban officials have said the crackdown was necessary to protect national security against opponents bent on undermining the island's communist system at the behest of the United States.

  Cuba's Catholic bishops issued a statement deploring the executions and the crackdown on dissidents. ''No one has the right to put in danger the lives of other people, like the hijackers did, but in the same manner, no one can decide that death must be inflicted on others as a remedy,'' the statement said in part.

  The Bush administration reacted quickly, calling the executions a reflection of totalitarianism.

  ''We are concerned that these executions may have been a result of summary proceedings,'' said Lou Fintor, a State Department spokesman. ``Summary proceedings are a hallmark of totalitarian dictatorships like Cuba. Due process allows an appropiate judicial process to carefully identify and punish serious crimes like hijacking and guard against manufactured charges based on political agendas as was done with the opposition groups.''

  South Florida's Cuban-American Republicans in Congress also condemned the executions.

  ''They were sentenced in kangaroo courts, tried for trying to flee Cuba and within hours shot to death,'' said Rep. Ileana Ros-Lehtinen.

  ''Castro's oppression constitutes a form of terrorism that cannot continue to be allowed to exist by the international community,'' said Rep. Lincoln Diaz-Balart.

  In Miami, Cuban exile leaders were furious. Joe Garcia, executive director of the Cuban American National Foundation, summed up the sentiment: ''They have murdered these poor people,'' he said. ``The summary trial and an execution without due process is murder, and the U.S government should indict Fidel Castro and his brother Raúl Castro and all the other thugs that govern that island.''

  In Key West, a U.S. Coast Guard spokesman said the service was on alert for any unusual activity in the Florida Straits arising from the executions. In times of tension in Cuba, South Florida officials worry about uncontrollable refugee boatlifts.

  Criticism also came from a few other countries -- but, by and large, foreign governments were silent. For example, Spanish Vice President Mariano Rajoy said the
  executions prove Castro ''is a tyrant,'' but Venezuelan President Hugo Chávez -- a Castro friend -- refused comment, saying he did not wish to interfere in Cuban affairs.

  Some Cuban experts said the executions and the dissident crackdown marked the start of a period of harshness in the island.

  Jaime Suchlicki, director of the Institute for Cuba and Cuban American Studies at the University of Miami, said Castro is trying to eliminate the opposition to solidify the Cuban Communist Party before retiring.

  ''The crackdown has to do with a plan by Castro of ending the opposition to pave the way for his brother and succession in Cuba,'' Suchlicki said.

  Castro has repeatedly said his brother Raúl, the defense minister, will be his successor.

  Besides those executed, another four men received life sentences: Maikel Delgado Aramburo, Yoanny Thomas González, Harold Alcalá Aramburo and Ramón Henry Grillo.

  Also sentenced in the same case were Wilmer Ledea Pérez, who received a 30-year term; Ana Rosa Ledea Ríos, five years; Yolanda Pando Rizo, three years; and Dania Rojas Gongora, two years.

  The group, reportedly armed with at least one pistol and several knives, seized the Baragua and its 50 passengers in Havana Bay April 2 and ordered the captain to sail north toward Florida.

  Later that day, the 45-foot ferry ran out of fuel in the Florida Straits. Officers on two Cuban Coast Guard patrol boats that chased the boat tried to persuade the hijackers to return to the island.

  The hijackers allegedly threatened to throw passengers from the boxy, flat-bottomed boat overboard but soon agreed to let the ferry be towed 30 miles back to Cuba's Mariel port for refueling.

  After the boat docked April 3 in Mariel, west of Havana, Cuban authorities gained control of the ferry and arrested the suspects. The arrests came after a French woman hostage jumped into the water to confuse her captors.

  The standoff ended with all the hostages, then the suspects, jumping into the water.

  The Baragua was hijacked a day after a Cuban passenger plane was hijacked to Key West by a man who allegedly threatened to blow up the aircraft with two grenades. The grenades turned out to be fake.

  Another Cuban plane was hijacked to Key West less than two weeks earlier.

  Cuba blames the hijackings on what it says is a lax attitude by American authorities toward Cuban hijackers who reach American shores.

  Hijackers who reached U.S. soil are now in U.S. custody, and U.S. officials deny they are being treated leniently.

  U.S. Attorney Marcos Jiménez in Miami has said Castro is ''wrong'' to say his office will treat the seven charged hijackers as ''heroes,'' noting they could face at least 20 years in prison for forcing the planes to Key West.

  Yet, U.S. District Judge James Lawrence King on Thursday agreed with a Key West magistrate that six of the hijackers could be released on bail because they pose no danger to the community or risk of flight.

  Immigration officials, however, say that even if the defendants are ordered released on bail, they would still remain in detention because of immigration violations.

  Herald staff writers Luisa Yanez and Jennifer Babson contributed to this report, which was supplemented by material from The Associated Press.