Venezuela's Chavez undergoing 'tough' chemotherapy - VP

A man walks in front of a poster of Venezuelan President Hugo Chavez outside a military hospital where he is being treated in Caracas February 25, 2013.

CARACAS (Reuters) - Venezuela's ailing President Hugo Chavez has been undergoing "tougher" new treatment for cancer including chemotherapy at the military hospital where he has been for the last two weeks, his vice-president said.

Speaking late on Friday after a Catholic Mass to pray for Chavez's health, Maduro described how the socialist president had personally given the order to leave Cuba in mid-February, two months after his latest cancer surgery there.

"He said 'I've taken the decision to return to Venezuela, I'm going to enter a new phase of complementary treatments, tougher and more intense, I want to be in Caracas,'" Maduro said.

"Do you know what the complementary treatments are? They are the chemotherapies applied to patients after operations," he added outside a chapel in the Caracas military hospital.

Apart from one set of photos showing Chavez in a Havana hospital bed, he has not been seen nor heard from in public since December 11 surgery in Cuba, his fourth operation since the disease was detected in mid-2011.

Furious at rumors swirling all week that Chavez may have died, Maduro said chemotherapy was only possible because his condition had improved in January after a delicate few weeks following the December operation.

Chavez's No. 2 urged Venezuelans to be on the guard against "rumor-mongers" and "destabilizers," saying right-wing politicians in the United States were in league with Venezuela's opposition to spread lies about his boss.

"Sadly, the opposition live in a world of hatred, wrongdoing, bad feelings and bad desires," Maduro said, adding that Chavez had become sick from over-working.

"He neglected his own body to give our people his work, his love, his life," Maduro said, confirming Chavez was still using a tracheal tube to breathe and was communicating with family and aides through written messages and other "creative" means.

Opposition leaders have accused Maduro of lying about Chavez's condition, and several dozen anti-government students have chained themselves up in public to demand proof that the president is alive and in Venezuela. (Reporting by Andrew Cawthorne; Editing by Vicki Allen)