Speaking on national television, an emotional Chavez said a return of cancer cells was detected during his most recent visit to Cuba for medical examination, and he will return to the communist-ruled island as early as Sunday for another round of surgery.

"During this thorough examination, they again detected some malignant cells in the same area as before," Chavez said.

He did not offer details, but his cancer was first detected in the pelvic area. Neither the Venezuelan leader, nor his Cuban doctors have ever disclosed what kind of cancer that was.

However, Chavez admitted that his Cuban medical team had conveyed to him a sense of urgency about the upcoming operation, which he said was "absolutely necessary."

"The doctor recommended that I undergo surgery yesterday (Friday) at the latest, or this weekend," he acknowledged. "But I did not agree and came back home."

Chavez returned from Havana on Friday after a 10-day stay in Cuba. He had not been seen in public for three weeks.

The Venezuelan leader also said that in the event he were incapacitated, his vice president Nicolas Maduro would step in and assume control of the government as required by the constitution.

But he also indicated he would like Maduro to replace him if something more serious were to occur and a new presidential elections were called.

"You choose Maduro as president of the republic," said Chavez addressing the Venezuelan people. "I am asking you this from all my heart."

The firebrand leader made the announcement despite frequent assurances on the campaign trail before his re-election in October that he had been cured of cancer.

Recurring bouts of cancer have dogged Chavez's presidency for the past couple of years, requiring to him spends weeks at a time being treated in Cuba.

The Venezuelan leader 58, has repeatedly claimed to have beaten an unspecified cancer in his pelvic region that was diagnosed in 2011 and shrugged off his illness to see off a unified opposition and secure another six-year term on October 7.

He had a cancerous tumour removed from near his pelvic region last year.

Chavez, who has been in power since 1999 and gained global prominence as an anti-American firebrand, appeared weak and subdued during the presidential campaign, but still managed to win another term that extends to 2018.

Prior to Saturday's surprise announcement, he had last been seen in public on November 15, and two weeks later he went to Cuba for treatment.

AFP