CARACAS (Reuters) - Venezuela's Hugo Chavez underwent surgery in Cuba on Tuesday for a cancer recurrence that has thrown his presidency into jeopardy and upended politics in the South American OPEC nation.
"My dear friend and colleague, Comandante Hugo Chavez, is going through the toughest times of his life," said Ecuadorean President Rafael Correa, a fellow leftist. "He is being operated on right now. It's a very delicate operation."
The 58-year-old socialist leader's surgery in politically allied Cuba was his fourth since mid-2011. Cancer was found again in his pelvic area soon after his October re-election, leading him to name a successor in case he is incapacitated.
Chavez's ministers have been parading on state TV to pledge loyalty to their boss but have given no details of his condition, which is treated virtually as a state secret.
A government source confirmed Tuesday's operation. Supporters were holding prayer meetings around the country in solidarity.
Having declared himself cured twice in the past, Chavez now worries the latest recurrence could end his tumultuous 14-year rule. He retains hope of recovering in time for the January 10 start of a new six-year term.
Chavez named his vice president and foreign minister, Nicolas Maduro, as a potential heir to lead his self-styled revolution in a nation of 29 million people with the world's largest oil reserves.
Maduro, 50, a former bus driver and union activist, lacks his boss's charisma and political flair but would represent policy continuity should he take over. He has already taken control of day-to-day government business.
'NOT A MONARCHY'
The naming of Maduro has irked some in Venezuela's opposition, who say voters - not Chavez - will decide who follows him if an election is held within 30 days of his leaving office, as required under the constitution.
"Venezuela is not a monarchy with a prince as heir," said one opposition leader, Antonio Ledezma.
Should an election be held, opposition flag bearer Henrique Capriles, who lost to Chavez in the October presidential ballot but scored a record 6.5 million votes for the opposition, could have a second crack at power.
In a newspaper interview on Tuesday, Capriles declined to speculate on a possible new presidential bid and repeated his best wishes to Chavez for recovery. But he criticized the secrecy surrounding the president's treatment.
"Venezuelans have the right to know," he said.
Chavez was assumed to be a patient once more at Havana's Cimeq hospital, though no official information on the situation was coming out of the communist-run Caribbean island.
The stakes are high for Cuba and various other socialist-run nations around Latin America and the Caribbean who depend on the Chavez government for subsidized oil and other economic aid.
Messages of support have poured in.
"He changed the history of Venezuela and of a large part of Latin America," said Correa, a central member of the Chavez-led Alba bloc of leftist nations in the region.
"He's in good spirits. You know what Hugo's like, always ready for tough battles with optimism and faith ... I'm not going to lie, we're very worried. It's a serious matter."
U.S. actor Sean Penn, one of Chavez's most prominent international supporters, joined a vigil in Bolivia. "He's one of the most impressive forces on the planet and we need to show him our love," Penn was quoted as saying by local media.
Chavez's health woes had sparked a rally in Venezuela bonds, given many investors' preference for a more business-friendly government in Caracas. Gains were trimmed slightly on Tuesday.
Western investors have increasingly shunned Venezuela under Chavez - especially given his nationalizations of large swathes of the economy - giving companies from China, Russia, Iran, Belarus and other allies a chance to grab footholds.
In London, veteran emerging market investor Mark Mobius said any change to a more market-friendly government in Venezuela would encourage him to invest there once more.
"Regime change has probably entered into a countdown phase," New York-based Jefferies' managing director Siobhan Morden said in a research note.
The health saga has once again eclipsed major national issues such as state elections on Sunday, a widely expected devaluation of the bolivar currency and a proposed amnesty for Chavez's jailed and exiled political foes.
"The nation is paralyzed," said Jorge Botti, head of the main private business group, Fedecamaras, urging the government to boost sales of dollars through its currency-control system.
The lack of greenbacks has left merchants struggling to import products and pushed the black market rate for the bolivar currency to four times its official rate of 4.3.
Venezuelans were expecting a currency devaluation around the New Year, though Chavez's illness has put this in doubt.
Maduro is a committed socialist who has espoused Chavez's views on the international stage for the last six years, including his vitriol against Washington.
He has indicated he would follow Chavez's main policies, including heavy state control of the economy.
"Currency controls have worked well, and yes, they can be improved. They are going to be improved," Maduro said.
(Additional reporting by Eyanir Chinea and Diego Ore in Caracas, Eduardo Garcia in Quito; Editing by Brian Ellsworth, Philip Barbara and Bill Trott)