Venezuelan President Hugo Chavez, an ailing icon of the Latin American left, was recovering after a successful cancer operation in Cuba, his vice president and chosen successor said.
A visibly moved Nicolas Maduro, to whom Chavez delegated power before undergoing a fourth round of cancer surgery in Havana, said Chavez would shortly begin a "post-operative phase" that would last several days.
"This operation ended correctly and successfully," Maduro said in an address to the nation in Caracas. "In these coming hours, we will be very attentive."
He described the six-hour operation as a "corrective surgery of a lesion" that occurred in the pelvic region, but did not elaborate.
Chavez, 58, flew to Havana for surgery on Monday after revealing to his stunned countrymen over the weekend that his cancer had returned just two months after his triumphant re-election to a six-year term.
The president was first diagnosed with the disease in June 2011. He had assured Venezuelans that he was cancer-free after three rounds of surgery, in addition to chemotherapy and radiation.
Significant aspects of his condition -- including the type, location and severity of his cancer -- have been kept secret over the past 18 months, fueling rumors and uncertainty in Venezuela.
Tareck El Aissami, a former interior minister and member of Venezuela's ruling party, had taken to the airwaves shortly after doctors began operating on Chavez to say that all was "going well."
Chavez's medical team expressed "optimism" as the cancer-stricken Venezuelan president went into surgery, while hundreds of faithful supporters gathered to pray that the longtime, omnipresent leader would live.
In the capital Caracas, Miriam Escobar stopped with her daughter at a mass being held in a downtown street to "pray for our commandant."
"We know that with faith you will succeed," Escobar said tearfully.
"I cry with joy and happiness for my commandant," Isabel Barrior, 50, told AFP as she took part in a candlelight vigil in Plaza Bolivar, in Caracas.
Chavez supporters held several Catholic masses and candlelight vigils across the country, praying for their leader to overcome the cancer that has haunted his rule for the past year and a half.
Venezuelan state TV showed hundreds of laborers demonstrating outside the presidential palace in Miraflores.
Maduro, speaking in Plaza Bolivar, urged the president's supporters to vote for allied candidates in December 16 regional elections, saying: "When we vote for your candidates, Chavez, we feel we are giving you a hug, or a kiss."
Chavez's latest health woes sparked concern among his leftist allies in the region, with Ecuadoran President Rafael Correa, who visited Chavez on Monday, expressing concern over the "very delicate operation."
"He is going through one of the most difficult moments of his life, this dear friend, colleague and Latin American leader, commandant Chavez," Correa said in the border town of Tulcan, Ecuador.
Chavez made clear before his departure to Havana that he was facing a serious setback, publicly naming Maduro as his preferred successor for the first time.
Without formally handing over the presidency, Chavez said he was delegating the country's "high political command" to Maduro while he was gone and said the vice president would succeed him if he became incapacitated.
Under Venezuela's constitution, elections must be held within 30 days if the president dies or is incapacitated.
Ecuador's Correa, a firebrand leftist economist who could succeed Chavez as leader of the Latin American left, on Monday flew to the Venezuelan's side in Havana where he found him in "great spirits."
"He gives us all strength," Correa said on Twitter.
Correa said he had also visited Cuban President Raul Castro and his predecessor Fidel Castro during his day-long stay in the Cuban capital.
With Cuba's backing, Chavez has taken the lead in forming a bloc of leftist Latin American governments that vehemently oppose the United States, and has cultivated friendly relations with US adversaries like Iran.
Members of the group include Bolivia, Cuba, Ecuador, Nicaragua and Venezuela.
Chavez is believed to be receiving treatment at the same Havana hospital where Fidel Castro has been cared for, which is seen as the communist country's best facility for complicated medical conditions.