Venezuelan President Hugo Chavez is "gaining strength" and entering a "new phase" of cancer treatment in Cuba, his anointed political heir said, as doubts about his health mount in Caracas.

Vice President Nicolas Maduro said in a statement on Sunday that the absent leader's "vital signs and organ function are stabilising, he is conscious and gaining strength for the next stage".

Maduro's remarks did not go far to address speculation among Venezuela's political foes that Chavez, who has not spoken publicly since December 10, is more ill than has been reported.

Chavez designated Maduro as his deputy before flying to Cuba for a fourth round of cancer surgery on December 11.

Opposition members have demanded Chavez speak to the Venezuelan people in state media if he is able, but he has not.

The Venezuelan government has been releasing only minimal information on the condition of Chavez, a 58-year-old former paratrooper who first came to power in the oil-rich country in 1999 and won another six-year term last October.

Maduro said that Chavez is "finishing the post-operative period and will enter a new phase of treatment", following his surgery.

National uncertainty

The charismatic and bombastic figurehead of the region's anti-American left could not attend his scheduled inauguration on January 10 because of his poor health, and his swearing-in ceremony has been postponed indefinitely.

The Venezuelan government has only admitted Chavez suffered complications, including a severe pulmonary infection that led to "respiratory insufficiency."

"We're always optimistic in the sense that sooner rather than later we will have the president here with us," Maduro said, adding that El Comandante was in good spirits and focused on his treatment.

Tensions are running high in Venezuela amid uncertainty over the future of Chavez.

Last week, the opposition seized on just a few words, Chavez's stamped signature on a decree, to demand he clarify how sick he is and what he can and cannot do.

The official government gazette published a decree dated Caracas and carrying the stamped signature of Chavez in which Elias Jaua was named as Venezuela's new foreign minister.

Henrique Capriles, a state governor whom Chavez beat in Venezuela's October presidential election, said it was puzzling that the decree carried the absent leader's name.

Officials have never disclosed the type or severity of Chavez's cancer, saying only that he has had a tumour removed from his pelvic region.

Source: Agencies