After rejecting rumors about Chavez's health earlier in the day, Vice President Nicolas Maduro and his wife, Attorney General Cilia Flores, were among several senior aides attending the ceremony in the outdoor brick chapel.
One of the president's daughters, Maria Gabriela, was among the worshipers while ordinary Venezuelans watched from behind a fence outside, praying and holding pictures of Chavez.
Chavez, 58, checked into the Carlos Arvelo Military Hospital on February 18 after spending two months in Cuba, where he underwent a fourth round of cancer surgery.
Aside from a set of pictures of him in his Havana hospital bed released on February 15, the once omnipresent leader has not come out in public in almost three months.
Maduro and other officials lashed out earlier against rumors that Chavez may be dead, branding them a campaign to destabilize the nation.
The science minister, Chavez's son-in-law Jorge Arreaza, said Chavez was "battling" but calm, with his doctors and family in the hospital.
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