The Cuban authorities have released a journalist who was serving a 15-year term for anti-government activities.
Paul Rivero, poet and critic of Castro, was released earlier in the week
Edel Jose Garcia, 60, is the sixth dissident known to have been freed by the government this week.
He was one of 75 activists given long jail terms last year in a crackdown by the regime on opposition voices.
His release comes as the European Union begins a review of its policy towards Cuba, prompting Havana to attempt to demonstrate human rights improvements.
About 20 more activists are reported to have been transferred to a hospital in the capital, leading to speculation that more could be released.
Three dissidents were freed on Monday and two on Tuesday, among them prominent journalist and poet Raul Rivero.
Esperanza Garcia, Mr Garcia's sister, told the Associated Press news agency that her brother had called her from Havana after being released on Thursday morning.
She said he had suffered emotional and health problems while in jail.
Elizardo Sanchez Santa Cruz, of the Cuban Committee for Human Rights and National Reconciliation, said Mr Garcia had undergone a medical examination before he was freed.
President Fidel Castro's government has not commented on the releases, but they come just days after Foreign Minister Felipe Perez Roque announced his country had resumed formal contacts with Spain.
Spain has recently been trying to improve relations between Havana and the EU, which imposed sanctions against Cuba in response to the crackdown.
Oscar Espinosa Chepe, Marcelo Lopez, Margarito Broche and Osvaldo Alfonso Valdes are among those to have been set free this week.
The EU and human rights groups have welcomed the releases but are calling for the remaining political prisoners to be let out.
Seven have been released for health reasons in recent months but another 62 remain behind bars.