"This process of recuperation ... will require a prudent time, as a result of the complexity of the surgical procedure, and also because of complications that came up in the surgery, when bleeding presented itself, requiring the adoption of corrective measures to permit its proper control," Information Minister Ernesto Villegas said in a televised address Thursday afternoon.
Vice President Nicolas Maduro said doctors had acted quickly to control the unexpected bleeding.
Speaking at a rally in northern Venezuela on Thursday evening, Maduro said Chavez's recuperation had "evolved from stable to favorable" but did not provide details about his long-term prognosis.
The news drew cheers and thunderous applause from those at the rally, which marked the end of campaigning for Sunday's regional elections.
Chavez, who first announced he was battling cancer in June 2011, underwent surgery Tuesday in Cuba.
He has not disclosed what type of cancer he has, and the Venezuelan government has released few details about Chavez's illness, fueling widespread speculation about his health and political future.
On Wednesday, the officials struck a more somber tone when discussing Chavez's treatment.
The information minister suggested Chavez might not be not be back in Venezuela in time for his scheduled inauguration, which is a month away.
Venezuelans "should be prepared to understand" if Chavez doesn't return to Venezuela before the inauguration on January 10, Villegas said.
"It would be irresponsible to hide the delicacy of the current moment and the coming days," he wrote in a post on the information ministry's website.
The title of his post -- "Chavez Will Live and Overcome" -- was similar to many official announcements since Chavez's illness was announced last year. But the message's tone was markedly different from previous ones.
"The president is a human being," Villegas said. "He underwent a difficult, complex, delicate operation. And now he is in post-operation, which is also difficult, complex and delicate."
Maduro said Wednesday that Chavez would face a "complex and difficult" recovery after the six-hour surgery. His voice cracked as he asked Venezuelans to remain united and pray for Chavez.
On Thursday, the vice president said some had criticized him for delivering the news with such a somber expression.
"Our faces are expressions of pain and worry and the most pure love that we feel for our Commander Hugo Chavez," he said. "He gave us the order to prepare the people for any circumstance. And we have followed that to the letter."
Chavez has undergone several surgeries and radiation treatment in Cuba in the past year and a half.
Health rumors dogged Chavez on the campaign trail this year but didn't stop him from winning re-election in October.
Over the weekend, as he prepared for the latest operation, Chavez said he wanted Maduro to replace him if "something were to happen that would incapacitate me."
It was the first time since his diagnosis that Chavez had specified a successor.
Neither Cuban nor Venezuelan authorities have disclosed where Chavez is being treated.
The government in Havana has remained tight-lipped about the treatment of their close ally, who sends Cuba millions of barrels of oil at deeply discounted prices.
Many Cubans are worried that Chavez's illness could mean an end to those generous subsidies. The island's economy never fully recovered after the Soviet Union cut their huge aid package following the fall of the Berlin Wall.
On Tuesday, panelists at a discussion about a new documentary on Chavez in Havana touched upon the leader's ill health.
Venezuela's military attache to Cuba appeared to tear up as he discussed Chavez's cancer.
"My commander in chief has been the man to take on problems," Col. Eldan Rafael Dominguez Fortty said. "We have overcome every obstacle, and now with this battle to survive, he will figure that out, too."
CNN's Patrick Oppmann reported from Havana, Cuba. CNN's Catherine E. Shoichet reported from Atlanta.