BY NANCY SAN MARTIN

  BARCELONA - More than 300 artists, intellectuals and politicians from around the world have joined an ''open letter'' campaign launched by a prominent magazine in Spain demanding the immediate release of Cuban government opponents recently sentenced to as many as 28 years in prison.

  The letter and signatures appear in the latest issue of Encuentro, a magazine based in Madrid that focuses on Cuban issues.

  The signers are predominantly Cuban exiles but also include influential figures such as union leaders and representatives of international organizations that work toward closer ties and development of Europe and Latin America. Even personalities with leftist views are included in the list of signers.

  Among the renowned figures who have joined the public condemnation of Fidel Castro's government are Nobel-winning author Günter Grass of Germany, Peruvian-born novelist Mario Vargas Llosa, and Spanish Oscar-winners Pedro Almodóvar and Fernando Trueba.

  Other famous names include musicians Willy Chirino and Paquito D'Rivera, columnist Carlos Alberto Montaner and actor Andy Garcia.

  A protest letter, also published in the latest issue of Encuentro, lashes out against the government and defends freedom of speech.

  The Cuban government last month rounded up opponents across the island. In summary trials earlier this month, 75 dissidents -- including one woman -- were convicted and sentenced to prison terms of between 6 and 28 years.

  The government accuses them of being mercenaries in the pay of the U.S. government who are working with American diplomats in Havana in an attempt to subvert the socialist system.

  The arrests and sentences have spurred strong condemnations from various nations and human-rights and press organizations.

  The Cuban government further enraged critics with Friday's execution of three men who hijacked a ferry boat in a failed attempt to reach the United States.

  The protest letter in Encuentro, a 7-year-old quarterly publication, calls the government's motives for the arrests ``insulting to human intelligence.''

  Dissidents who express their opinions, the letter states, are not ``spies or traitors to the homeland but rather citizens concerned for the present and the future of the
  homeland.''

  The letter states that it is not just for a government to attempt to stomp out human desire or punish peaceful activists. It accuses the Cuban government of gross violation of human rights and characterized the regime as one that ``promotes hate, lies and contributes to maintaining its citizens unaware and misinformed of what is happening in and outside of Cuba.''

  The full text of the letter and the list of signatures calling for the immediate release of prisoners can be found at www.cubaencuentro.com