"It is clear Chavez does not have the capacity to fully exercise his power ... This is a very dangerous, nefarious precedent," Roberto Enriquez, national president of the COPEI Christian Democrat opposition party, told reporters.
State news agency AVN released four new photographs of the 56-year-old president on Saturday it said were taken on Friday while he took a 10-minute morning walk in Havana.
In the pictures, Chavez looked pale and was wearing a blue sports T-shirt and tracksuit trousers. (http://bit.ly/irxzBm)
In one he was with Venezuelan Foreign Minister Nicolas Maduro and in the others he was holding hands with two of his daughters and then standing and talking with the pair.
Chavez's cancer, which the charismatic socialist leader revealed on Thursday in a televised speech from Havana, has convulsed politics in South America's biggest oil exporter ahead of a presidential election next year.
In an interview late on Saturday with a local TV network, Maduro gave details of the operation that extracted the cancerous tumor, saying it was excised from the same pelvic region from which an abscess had previously been removed.
"All his organs were checked, which were in a perfect state, but it was a pretty serious operation," he said.
COPEI's Enriquez said Chavez's absence for treatment in Cuba threatened the country's security and sovereignty.
"The security of the state cannot be handled from outside the national territory ... Affairs of state are being discussed in foreign government installations," he said.
Vice President Elias Jaua and Venezuela's military chiefs have rejected calls for any temporary delegation of Chavez's powers. They argue the National Assembly dominated by the president's supporters has already approved his absence.
Chavez's illness has underlined the lack of an obvious successor to the populist Venezuelan leader whose personalized style of government has dominated the OPEC country since 1999.
It has also stoked fears of a power vacuum and political infighting among the fractious ranks of his supporters.
Neither Chavez nor his government has given a firm date for his return, fueling conjecture about what kind of cancer he has and how long it could take him to recover. Media reports have speculated he has either colon or prostate cancer.
"He will come when his doctors say it is time," Jaua told Reuters at preparations to mark the 200th anniversary of Venezuela's independence from Spain -- a celebration on Tuesday that Chavez would dearly love to attend.
Maduro said more information about Chavez would be given as it became available in the coming days and weeks.
"He's started an almost miraculous and ascending process of physical recovery," Maduro told Televen TV. "The Bolivarian government presided by President Chavez is operating."
Analysts say any diminishing of the former soldier's visibility or volubility could reduce his ability to rally support for the 2012 election.
"The revolution and the new socialism are words that without President Chavez have little meaning for a broad number of people, with many periphery supporters likely to shift toward the opposition," global banking group RBS said.
With polls showing the popularity of Chavez's government being eroded by economic woes, high crime rates and problems like chronic power outages, next year's vote is likely to be crucial for Chavez in a long career that has been marked by a string of victories at the ballot box and the projection of his leftist policies around the world.
On the streets of Caracas on Saturday, debate swirled over just how ill Chavez might be and when he would come back.
"Cancer is a very serious illness and he looked very bad to me, very thin, pale, he didn't look like the same old Chavez," said Yiletsi Velasco, a 53-year-old housewife.
Newspaper vendor Wilmer Rojas was more upbeat.
"Chavez is going to be back faster than some people think. I see a lot of people talking, but you'll see Chavez will be back. Not even cancer can bring him down," he said.
One source close to the Venezuelan medical team following his recovery has said the diagnosis revealed a cancer that required aggressive treatment that could take several months.
A wing of the Military Hospital in Caracas was being prepared to receive him when he returns, the source said.
Caracas: Venezuela's opposition said on Saturday President Hugo Chavez's prolonged convalescence from cancer in Cuba put the country's security and sovereignty at risk and it stepped up calls for him to delegate his powers.
First Published: Sunday, July 03, 2011, 14:32