Defying foreign pressures to ease political controls, Cuba put four opposition leaders on trial behind closed doors Monday after a massive weekend crackdown on about 90 dissidents to avert public protests.

Police enforcing the largest roundup of dissidents since 1996 arrested 42 opposition figures and warned 46 others that they would be jailed if they left home during the trial, human rights activist Gerardo Sanchez said.

International human rights groups condemned the trial as another sign of government intolerance, following the adoption last month of a law making it a crime to ``support, facilitate or collaborate with'' U.S. policy on Cuba.

``This trial is fully consistent with the government's current policy of closing off even the smallest spaces available to dissidents, said Jose Miguel Vivanco, Americas regional director for Human Rights Watch.

Police kept Western diplomats and reporters 300 feet from the Havana courthouse where Vladimiro Roca, Marta Beatriz Roque, Felix Bonne and Rene Gomez Manzano were tried. Relatives were allowed in, but journalists reported seeing police take away at least three people from the building.

The top U.S. diplomat in Cuba, Michael Kozak, turned up outside the courtroom in the Marianao neighborhood ``as an act of solidarity'' and charged that ``the result of this trial has already been decided.

``It is obvious that this system cannot withstand scrutiny, not even from some blocks away. This is not a good day for Cuban justice, said Kozak, head of the U.S. Interests Section.

The four defendants became some of Cuba's best-known dissidents after King Juan Carlos of Spain, Pope John Paul II, the European Union and several major human rights groups began pleading for their freedom in 1997.

Police bent on averting any public demonstrations around the trial launched the biggest crackdown on dissent since the 1996 arrest of the Concilio Cubano leadership, said Sanchez, of the Cuban Commission for Human Rights and Reconciliation.

Reached by phone by friends in Havana, Oswaldo Paya, head of the Christian Liberation Movement, reported that a policeman posted at his door was keeping him from leaving home.

Earlier protests

Two trials of dissidents last year sparked small but highly unusual protests by supporters of the defendants. Some of the protests were recorded on video by foreign television cameras and widely reported abroad.

Among those detained over the weekend were opposition leaders Jesus Yanez, Pablo Silva and Lazaro Coles, at least four independent journalists, and Marieta Menendez and Ileana Someillan, activists in the Mothers for Democracy group.

Reported missing by relatives and presumed detained was Cuba's best-known independent journalist, Raul Rivero, a poet who reports often for El Nuevo Herald.

The four defendants who went on trial Monday, known as the Working Group for Internal Dissidence, are charged with ``acts against the security of the state, related to the crime of sedition.

Their indictments accuse them of attempting to disrupt elections and scare away foreign investors, lying about the economy, receiving ``support'' from the U.S. government and having links to ``terror'' groups in Miami.

Critics of government

Defenders say their only crime was opposing the government and writing a harsh critique in 1997 of Cuban President Fidel Castro and the Communist Party's monopoly on power, titled ``The Homeland Belongs to Us All.

Kozak told reporters outside the courtroom that Washington's policy of supporting nongovernment organizations in Cuba is designed not to subvert Castro's government but to promote the growth of democracy.

Prosecutors have requested five-year prison terms for three of the defendants and a six-year term for Roca, one of Cuba's best-known dissidents.

A former air force pilot, Roca is the son of the late Blas Roca, a longtime communist labor leader. A government-run brigade of young toughs sometimes used to quell street disturbances is named after Blas Roca.

Diplomats kept away

Also blocked from attending the trial were diplomats from Spain, Canada, Great Britain, Germany, the Czech Republic, Poland, Sweden, Switzerland and South Africa.

The Cuban American National Foundation called on the U.S. Senate Monday to condemn Castro, saying ``the civilized world has been reminded once again . . . of Fidel Castro's brazenness and rigidity.

But Vivanco, of Human Rights Watch, said the trial showed that Cuba ``can thumb its nose at the world only because of the great division between the U.S. policy of isolation and the predominant world view of engagement.

``Castro can give himself this luxury because the United States is so alone in its policy that the split with the rest of the world gives him room to maneuver, he said.