* President suffering complications after cancer surgery
* Chavez has not been seen nor heard from in 3 weeks
* Rumors swirl about his condition, fuel bond rally
By Daniel Wallis and Diego Ore
CARACAS, Jan 3 (Reuters) - Vice President Nicolas Maduro returned to Venezuela on Thursday after visiting Hugo Chavez in hospital in Cuba, but gave no new details on the cancer-stricken president as rumors grow about his condition.
Flanked by senior government figures including Diosdado Cabello, the head of the National Assembly, Maduro toured a coffee production plant in Caracas - the type of visit that the president made frequently before he fell ill.
Chavez, 58, has not been seen in public nor heard from in more than three weeks and officials say the socialist leader is in delicate condition after suffering complications following his fourth cancer operation in just 18 months. But they have offered very few details.
"In the last few hours we were with President Hugo Chavez, bringing him the encouragement and strength of the Venezuelan people," Maduro said on Thursday. He said Cabello, Oil Minister Rafael Ramirez and Chavez's elder brother Adan, among others, had all been with the president in the Cuban hospital.
Venezuelan bonds rallied to 2008 highs on Thursday on rumors about Chavez's health.
In scenes that recalled Chavez's hours-long televised visits to building sites, hospitals and oil refineries, Maduro told workers at the nationalized Fama de America factory that there was no "transition" taking place in the country.
"The only transition in Venezuela is the transition to socialism," he said in comments carried live by state television.
"It began six years ago, ordered by Comandante Hugo Chavez as chief and president, elected, re-elected and ratified, much as it pains the bourgeois hucksters and the right, who have done so much damage to our fatherland."
Chavez's abrupt exit from the political scene would be a huge shock for the South American OPEC nation. His oil-financed socialism has made him a hero to the poor majority but critics call him a dictator.
He is still set to be sworn in on Jan. 10, as spelled out in the constitution. If he were to die or had to step aside, new elections would be held within 30 days, with Maduro running as the ruling Socialist Party candidate.
Chavez's condition is being watched closely by Latin American allies that have benefited from his generous assistance, as well as Wall Street investors who are attracted to Venezuela's lucrative and widely traded debt.
Last year, Chavez staged what appeared to be remarkable comeback from the disease to win re-election to a new six-year term in October despite being weakened by radiation therapy. But he returned to Cuba for more treatment within weeks of his win.
Officials have said he suffered unexpected bleeding and then a respiratory infection after a six-hour operation on Dec. 11.
Top Socialist Party officials have suggested that his inauguration could be postponed indefinitely to accommodate his recovery.
The opposition has insisted that the government should stick to the Jan. 10 date, and on Thursday one opposition leader said they should form an official commission to visit Cuba and assess the president's condition for themselves.