Agee quit the CIA in 1969 after 12 years working mostly in Latin America at a time when leftist movements were gaining prominence and sympathizers. His 1975 book "Inside the Company: CIA Diary," cited alleged CIA misdeeds against leftists in the region and included a 22-page list of purported agency operatives.
Granma, Cuba's Communist Party newspaper, said Agee died Monday night and described him as "a loyal friend of Cuba and fervent defender of the peoples' fight for a better world."
Bernie Dwyer, a journalist with state-run Radio Havana, said in a Tuesday message posted to a Cuba e-mail group that Agee's wife called him to say he had died after ulcer surgery in a hospital where he has he been since Dec. 15.
"He had several operations for perforated ulcers and didn't survive all the surgery," Dwyer wrote, adding that Agee was cremated Tuesday and that friends planned a memorial ceremony for him Sunday at his Havana apartment.
Agee's U.S. passport was revoked in 1979. U.S. officials said he had threatened national security. After years of living in Hamburg, Germany - occasionally underground, fearing CIA retribution - Agee moved to Havana to open a travel Web site.
The site, cubalinda.com, is designed to bring U.S. tourists to Cuba, offering package tours and other help that is largely off-limits to Americans because of the U.S. trade embargo. Agee opened the site in 2000 with European investors and a state-run travel agent as his partners.
There was no mention of Agee's death on the site Wednesday.
The author of several other books besides "Inside the Company," one of Agee's last essays was published in Granma International newspaper in 2003 and came shortly after a Cuban government crackdown led to the arrest of 75 leading dissidents and political activists.
"To think that the dissidents were creating an independent, free civil society is absurd, for they were funded and controlled by a hostile foreign power and to that degree, which was total, they were not free or independent in the least," he wrote.
Agee has been accused of receiving up to $1 million in payments from the Cuban intelligence service. He denied the accusations, which were first made by a high-ranking Cuban intelligence officer and defector in a 1992 report.
Barbara Bush, the wife of former President George H.W. Bush - himself a one-time CIA chief - in her autobiography accused Agee's book of exposing a CIA station chief, Richard S. Welch, who was later killed by leftist terrorists in Athens in 1975. Agee, who denied any involvement in the killing, sued her for $4 million for defamation, and she revised the book to settle the case.
Agee's actions in the 1970s inspired a law criminalizing the exposure of covert U.S. operatives.
But in 2003, he drew a distinction between what he did and the exposure of CIA officer Valerie Plame, the wife of former Ambassador Joseph C. Wilson IV, a prominent critic of President Bush's Iraq policy.
"This is entirely different than what I was doing in the 1970s," Agee said. "This is purely dirty politics in my opinion."
Agee said that in his case, he disclosed the identities of his former CIA colleagues to "weaken the instrument for carrying out the policy of supporting military dictatorships" in Greece, Chile, Argentina, Uruguay and Brazil.
Those regimes "were supported by the CIA and the human cost was immense: torture, executions, death squads," he said.