Venezuelan President Hugo Chavez has been receiving chemotherapy since recovering from a severe respiratory infection in mid-January and “continues his battle for life”, his vice president said.

Vice President Nicolas Maduro disclosed for the first time that Mr Chavez began chemotherapy following his fourth round of cancer surgery in Cuba in December.

“He has strength that is superior to the treatments that he is receiving and he is in good spirits, battling, receiving his treatments,” he said after a Mass for Mr Chavez, who is being treated at a Caracas military hospital.

When he went into the operating room in Havana on December 11 Mr Chavez told his aides that there was a “possibility that he would not come out” alive, but he survived it, said Mr Maduro.

The vice president quoted Mr Chavez as saying he decided to return to Venezuela because he was entering “a new phase” of “more intense and tough” treatments and wanted to be in Caracas for them.

Mr Maduro, the leftist leader’s political heir, rejected a wave of rumours that Mr Chavez was dead or on his deathbed and lashed out at the opposition, which accused him of lying about the president’s condition.

Opposition leader Henrique Capriles said in a tweet: “We’ll see how they explain to the country in the (coming) days all the lies they’ve been telling about the president’s situation.”

Mr Chavez has not been seen nor heard from since going to Cuba for his fourth cancer surgery, except for a set of “proof of life” photos released on February 15 while he was still in Havana.

The leader’s condition was extremely delicate over New Year’s as he battled a respiratory infection that required a tracheal tube, said Mr Maduro.

He said: “In mid-January he was improving, the infection could be controlled, but he continued with problems of respiratory insufficiency. Afterward, there was a general improvement, and the doctors along with President Chavez decided to initiate complementary treatments.

“You know what the complementary treatments are, right? They are chemotherapy that is applied to patients after operations.”

The opposition says Mr Chavez should either be sworn in for the new term he won in the election or declare himself incapable and call a new election. The constitution says he should have been sworn in on Jan. 10, but Venezuela’s Supreme Court said it was OK to wait.