Hugo Chavez undergoes cancer surgery in Cuba
Information Minister Ernesto Villegas, reading a statement on Venezuelan television, said the surgery was under way and that beforehand Chavez had expressed "absolute confidence he will overcome the obstacles that have emerged in the path of life."
It is the fourth cancer-related operation that Chavez has undergone since June 2011.
Tareck El Aissami, a close confidant of Chavez, later told state television in Venezuela the operation was progressing without any problems.
"Everything is going well," El Aissami said.
Cuban officials have been silent on Chavez's surgery with news of developments coming from the government in Caracas. It is unclear if Venezuelan officials will announce when the surgery was completed.
The Venezuelan president announced on Saturday that he needed to have surgery again after tests showed "some malignant cells" had reappeared in the same area of his pelvic region where tumors were previously removed.
On the streets of Caracas, Venezuelans on both sides of the country's deep political divide voiced concerns about Chavez's condition and what might happen if he doesn't survive his illness.