Venezuela's government says President Hugo Chavez is suffering from a "severe" respiratory infection.
The 58-year-old president is reported to be in delicate condition as he battles an undisclosed form of cancer in his pelvic area.
"After the delicate surgery of this past December 11, Commander Chavez has faced complications as a result of a severe lung infection," said Information Minister Ernesto Villegas, reading a government statement on television late on January 3.
"This infection has caused a respiratory insufficiency that requires Commander Chavez to comply strictly with the medical treatment."
The statement gave no further details about Chavez's condition.
The complications follow his latest operation, which is his fourth surgery in 18 months.
The Socialist president was reelected in October to another six-year term despite being weakened by radiation therapy. Two months later, he announced that the cancer had come back.
He hasn't been seen in public since before his December 11 operation in Cuba.
The opposition has demanded that the government provide more details about his condition.
But the government statement expressed confidence in Chavez's medical team and accused the international media of conducting "psychological warfare" regarding Chavez's condition to destabilize Venezuela. It gave no details to back up the claim.
After visiting Chavez at the Havana hospital, Vice President Nicolas Maduro said on January 3 that Chavez "is conscious of all the circumstances he's living through, which are complex circumstances."
He said Chavez was "conscious of the battle he is fighting and he has a spirit of battle as always, with the strength he always has, with the energy he always has, with confidence and security and that's what he has told us to tell our people. He is fighting in the company of his relatives, in our company."
Chavez's health troubles have raised questions about whether he will be healthy enough to return to Venezuela to be sworn in as president on January 10.
Officials, however, have urged Venezuelans not to heed rumors that the president could be close to death.
If he were to die or to step aside, new elections would be held within 30 days, with Maduro running as the ruling Socialist Party candidate.
With reporting by Reuters, AP, and AFP