The El Nuevo Herald report cites unidentified sources but said Chavez -- who has been receiving chemotherapy for an undisclosed type of cancer -- entered a military hospital in the Venezuelan capital on Sept. 27.
Chavez, meanwhile, called state television on Thursday and urged Venezuelans to "pay no attention to rumors," apparently referring to the newspaper's report.
He said he is taking steroids and other medicines as he recovers from chemotherapy treatments for cancer. He said he is working at "half throttle" while undergoing physical and medical therapy.
He is likely to undergo dialysis and may be transferred to a private hospital to receive better treatment, according to the report.
One source told the paper that the leader was in "fairly serious overall condition," the AFP reported.
Andres Izarra,Venezuela's information minister, appeared to deny the report in a posting on Twitter.
"Those who should be admitted are the journalists of the Nuevo Herald, except into a madhouse (instead of a hospital)," the post reportedly said.
But the country's silence about the leader's illness appears to only add to the speculation about its severity. This week, Venezuela informed the United Nations that Chavez, would not address the General Assembly in New York, prompting questions about the leader’s health.
Chavez, who had a large tumor removed by doctors in Cuba in June, told state television last week he had finished chemotherapy in Cuba and was anticipating a "full recovery." He recently underwent his fourth round of chemotherapy in Cuba, and described the treatment as “highly successful.”
The Associated Press contributed to this report.