Four top Cuban dissidents, jailed for more than a year after they issued a scathing critique of the Communist government, were finally charged Thursday with sedition and acts against the state's security.

Prosecutors asked for a six-year sentence for Vladimiro Roca and five years each for Marta Beatriz Roque, Felix Bonne and Rene Gomez Manzano, said Miami human-rights activist Ruth Montaner.

The four are among Cuba's best-known dissidents. Amnesty International and Human Rights Watch have appealed to President Fidel Castro to free them, and several European human rights groups have made pleas on their behalf.

A trial could come at any time and a conviction is virtually certain, said Montaner, who has kept in touch by phone with relatives of the four.

The four leaders of the Internal Dissidence Working Group were arrested July 16, 1997, after they published a withering attack on the Communist system titled The Homeland Belongs to All.

The document challenged the ruling Communist Party's claim to represent the best interests of Cuba's 11 million people and attacked the party's decades of stewardship of the economy as a failure.

The document was later endorsed by several exile groups in Miami.