HAVANA (Reuters) - An independent Cuban journalist walked out of prison to become the sixth ailing government opponent freed after a crackdown on dissent last year, opposition sources said on Thursday.

Manuel Vazquez Portal, 52, who suffers from respiratory problems, was one of 75 dissidents sentenced to an average of 19 years in prison after daylong trials in April 2003.

"He arrived home around midnight and looked well," said Laura Pollan, wife of still-imprisoned Hector Maseda.

Academic Roberto de Miranda, 62, who had been sentenced to 20 years behind bars, was also released on Wednesday. He suffers from a heart condition.

The first of the six was released in April and all were conditionally freed for health reasons.

Last year's crackdown, considered the harshest in decades, provoked an outcry from numerous governments, Pope John Paul , and other prominent people.

Communist authorities accused the 75 opponents of working with the United States to overthrow President Fidel Castro's government, a charge they denied.

The repression led to a dramatic deterioration of Cuba's relations with the European Union , which continues to demand all 75 prisoners be freed.

In a separate case, four other dissidents were unexpectedly released this month after being held for more than two years without trial.

But another 16 government opponents have been jailed since April, according to veteran human rights activist Elizardo Sanchez.

Amnesty International reported this year that there were 88 prisoners of conscience in Cuba.