(Reuters) - Venezuela's President Hugo Chavez made a theatrical return home on Friday after medical treatment in Cuba, walking and joking in a first public appearance for three weeks that quashed rumors he may have been at death's door.

"So, where's the party?" an ebullient and robust-looking Chavez said after flying in before dawn to the surprise and delight of supporters.

"I'm happy and enthused to be back again," he told beaming ministers after walking unaided down the steps from his plane at the international airport outside Caracas.

The 58-year-old socialist leader has had three cancer operations in Cuba since mid-2011 and returned to Havana ten days ago to receive "hyperbaric oxygenation" - a treatment normally used to alleviate bone decay from radiation therapy.

Speculation had been rife that he may have suffered a recurrence of the disease, and one local journalist had said he was confined to a wheelchair.

Earlier this year, Chavez declared himself "completely cured" and went on to win re-election comfortably in October.

Amid a barrage of rumors fed by the opposition, officials had maintained that his latest visit to Cuba was just a scheduled follow-up to the radiation therapy he underwent in the first half of 2012.

Supporters celebrated the return of a man who has dominated the South American OPEC nation since he first won election in 1998. He wore a blue and white tracksuit and flew with relatives and aides including Vice President Nicolas Maduro.

"YEEESSSS!!!!," tweeted Eva Golinger, an American-Venezuelan lawyer close to the Chavez government.

"Chavez is back and has shown up all the rumor-mongers, necrophiliacs, gossips and ill-thinkers ... Welcome comandante."

Chavez looked relatively well, moving with ease and chatting for 15 minutes on the runway, although he remains puffy-faced as he has been since the radiation treatment.

QUESTIONS LINGER, BONDS FALL

Chavez's return gives him a week to campaign for Venezuela's December 16 state elections, where his ruling Socialist Party is hoping to use the momentum of the presidential victory to win back some opposition-held governorships.

The opposition, however, is hoping that discontent with grassroots issues like crime, power-cuts and cronyism will enable it to at least hold the seven states it controls out of Venezuela's 23.

Speculation over Chavez's health is unlikely to end, given the scant details given by the government.

Doctors say hyperbaric oxygenation is a treatment normally given in different sessions over several months, meaning he could return to Cuba again soon.

They also say nobody can declare themselves cured of cancer until a couple of years have passed without recurrence.

The president had dearly wanted to attend a Mercosur summit in Brazil on Friday, to celebrate Venezuela joining the regional trade bloc this year, so his absence from that maintained a question mark over just how well he is.

News of Chavez's trip to Cuba had prompted a Venezuelan bond rally given Wall Street and Western investors' preference for a more business-friendly government in Caracas.

But in early trading on Friday, following news of his return, Venezuela's global bonds fell 1.81 pct in price, according to returns tallied by the J.P. Morgan Emerging Markets Bond Index Plus (EMBI+).

Bonds had risen 6.2 percent so far this month to Thursday.

Opponents criticize Chavez for secrecy over his health and preferring Cuban doctors to Venezuelans.

"His whole absence has been a black hole of misinformation," opposition legislator Tomas Guanipa told local media.

"Any president should give account to his people, it is an obligation to give health details. When you are transparent and responsible, and recognize you are there to serve the people not boss them, the logical thing is to say what is going on."

Chavez has chosen to be treated in Havana due to his friendship with Cuba's past and present leaders Fidel and Raul Castro, plus the discretion he is guaranteed thanks to the Communist government's strict controls on information.

Cuba's Communist Party newspaper published photos showing Raul Castro bidding farewell to Chavez at Havana airport. Chavez said he had met Fidel Castro during his stay.

(Additional reporting by Jeff Franks in Havana, Mario Naranjo, Andrew Cawthorne and Marianna Parraga in Caracas, and Walker Simon in New York; Writing by Andrew Cawthorne; Editing by Daniel Wallis and David Storey)