Accompaning the photos in the Juventud Rebelde newspaper was a statement attributed to the Cuban president that said: "I feel very happy. For all those who care about my health, I promise to fight for it."
Although Castro was pictured in apparently good health, the road to recovery is not yet over.
The statement said: "To say that the objective stability has considerably improved is not making up a lie.
"To affirm that the recovery period will take a short time and that there is no risk would be absolutely incorrect."
However, the leader urged his public to be optimistic and be ready to face any adverse news.
"To the people of Cuba, infinite gratitude for your loving support. The country is marching on and will continue marching on perfectly well," the statement said.
Raul's first
Castro's brother, Raul, also made his first public appearance on Sunday since becoming acting president.
Raul Castro met Hugo Chavez, the Venezuelan president, with a military salute and a hug at Havana airport.
It was the Cuban defence minister's first appearance since his brother temporarily ceded power to him on July 31 due to surgery to stop intestinal bleeding.
Chavez, a top ally, flew to Havana to mark the elder Castro's birthday.
State secret
Details of Castro's health are treated as a state secret but on Saturday the communist party's daily newspaper, Granma, reported that he was "up and about".
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Raul Castro became acting president on July 31 |
"Someone who visited the commandante ... said he witnessed how the head of the revolution, after receiving a little physical therapy, walked in the room and later, sitting in a chair, engaged in an animated conversation," Granma reported.
No one knows if he will make an appearance or a speech on his birthday on Sunday but Cubans are being asked to carry out voluntary work in tribute to the president.
Official media called for "a huge productive day this Sunday as a dignified present to Fidel and the motherland".
Cubans are also being urged to donate blood and clean up their neighbourhoods.
Musical tribute