NEW YORK — Fidel Castro showed himself to be alive and well yesterday, appearing in a Cuban newspaper on his 80th birthday for the first time since he announced he was handing power to his brother, Raul Castro, while he recovered from intestinal surgery.

The communist leader — the world’s longest-serving head of government and the leader of the Americas’ only communist country for almost 48 years — was photographed wearing a red-and-white striped tracksuit, sitting upright on a bed and holding up a copy of Granma, the Communist Party daily, to prove the picture was current.

Cubans have rarely seen the leader of La Revolucion wearing anything other than khaki fatigues.

“I feel very happy,” the convalescing leader told Cubans in a message alongside his photograph in the Juventud Rebelde newspaper.

Two pictures show him speaking on the telephone.

“To say the stability [of my condition] has improved considerably is not to tell a lie,” Mr. Castro said in a written statement.

“To say that the period of recovery will be short, and there is now no risk, would be absolutely incorrect.”

The statement added: “I suggest you be optimistic and, at the same time, always prepared to receive bad news.

“The country is running well and will continue to do so.”

Mr. Castro has not been seen in public since July 26, a national holiday.

Authorities announced on July 31 that he had temporarily ceded power to his brother, Raul Castro, following surgery.

Details about Mr. Castro’s health remain a secret, but, according to the state press, he is now walking and in good spirits. As if to reassure those not quite convinced, Raul Castro, 75, appeared for the first time since he was handed control of the country, with Fidel Castro’s greatest ally in Latin America, President Chavez of Venezuela.

Mr. Chavez said he was bringing a “nice gift, a good cake” to celebrate “the 80 years of this great figure of America and our history.”

Although formal birthday celebrations have been put off until December, 3,000 Cubans attended a five-hour concert in Mr. Castro’s honor on the “anti-imperialist stage” opposite the American diplomatic mission on the Havana seafront.

Throughout the event, they chanted: “Fidel, Fidel, long live Fidel.”

The Russian president, Vladimir Putin, described Mr. Castro as one of the most “brilliant” political leaders of his era in a birthday telegram to the veteran Cuban president, the Kremlin said.

“In Russia, we know you well as one of the most brilliant and authoritative political men of current times,” Mr. Putin said.

Mr. Castro can bask in a sense of satisfaction that his legacy will live on in Latin America long after he is gone.Mr. Chavez appears as the leader of a new generation of left-wing Latin American revolutionaries, growing increasingly confident after brutal repression in the 1970 and 1980s.

In recent years, Mr. Chavez, whose country’s oil has been key to keeping the Cuban economy afloat, is seen across Latin America as the man who will take up Mr. Castro’s cause when he is gone.

The two men have become increasingly close in recent years, and Mr. Chavez reportedly received a letter from Mr. Castro in recent days.

Mr. Chavez has hailed Mr. Castro as a leading partner in the Bolivarian Alternative for the Americas, a counterweight to the Washington-backed Free Trade Area of the Americas. Venezuelan oil is pumped to Cuba, and Mr. Castro has supplied Venezuela with 20,000 teachers and doctors.

Another leftist leader, President Morales of Bolivia, is an avowed admirer of Cuba’s affordable education and medical care.