The crowd, including various leaders at the more militant end of the Democratic Unity opposition coalition, waved banners that said: “Give us the truth!” and “Stop lying!”
With Mr Chavez unseen, apart from one set of photos, since a 11 December cancer operation in Cuba, Venezuelans are on edge waiting for developments amid a sea of rumours.
Officials say Mr Chavez is in a Caracas military hospital after returning from Cuba two weeks ago, battling for his life. Though he is breathing via a tracheal tube, unable to speak, and undergoing chemotherapy, the president continues to rule via written and other communications, they say.
However, many believe the president is already dead.