Caracas, Feb 14 (IANS/EFE): Venezuelan President Hugo Chavez is undergoing "very complex and tough" medical treatment in Cuba, where he has been hospitalized since Dec 11 after undergoing cancer surgery for the fourth time, Venezuelan Vice President Nicolas Maduro said Wednesday.

"Our commander is being subjected to supplementary treatment, as we have reported, treatments (that are) very complex and tough," Maduro said at an event broadcast by state-run television after announcing that he had just returned from Cuba.

Maduro said that Chavez is "undergoing alternative treatments ... but they are complicated and difficult treatments that must - at some point - end the cycle of his illness".

Chavez was operated last Dec 11 for a tumour in his pelvic region - the specific nature of which has never been made public - but experienced complications as a result of excessive bleeding, the government said.

In the last report provided about the president's condition, Jan 26, Communications Minister Ernesto Villegas said that Chavez's general progress was "favourable" after overcoming a serious respiratory infection although he continued to have "a certain level of respiratory insufficiency", for which he was continuing to receive treatment.

Maduro said that he had traveled to Cuba as different top government officials have done - although on this occasion his trip was not announced either before or during his stay on the island - to "first and foremost attend to the commander president's family".

He said that on these visits he expresses to Chavez's family members "the permanent solidarity ... (and) the strength of the entire Venezuelan people".

Such trips also allow him to "share and exchange" information with Chavez's medical team.

The Venezuelan leader, 58, who came to power in 1999, has not been seen or heard from publicly since Dec 10 when Venezuelan state-run television broadcast several images of him before he left Caracas to undergo surgery in Cuba.