Several thousand demonstrators drew chalk silhouettes evoking murder scenes around themselves and lay across the avenue in the latest opposition protest sparked by the recent high-profile kidnapping murders of three schoolboys.
"You go out into the street in Venezuela and you're scared," said Ana Virginia Gil, 23, holding a banner bearing the photograph of a friend she said was killed after being kidnapped for a month in the western state of Anzoategui.
The execution-style killings of three young brothers, kidnapped on their way to school, earlier this month has heightened fears over violent crime, especially among middle- and upper-class opponents of the leftist president.
In protests that followed the killings, a local newspaper photographer was shot and killed by an unknown assailant who sped away on a motorbike.
Chavez, a self-proclaimed socialist who survived a brief coup in 2002, has won over much of the No. 5 crude exporter's poor by channeling cash from oil exports into social programmes.
But critics say he has become more authoritarian and not tackled basic issues including crime and corruption.
Although Chavez is likely to win a landslide victory in December elections, the country's splintered opposition is homing in on crime as a potential Achilles heel.
While Chavez's government has moved quickly to arrest suspects in the brothers' murders, it accuses the opposition of playing up violent crime for political motives.
A smaller group of pro-Chavez students dressed in red staged a rival march, many blaming high crime rates on poverty they said was generated by the capitalist system which Chavez, a friend of Cuba's Fidel Castro, has vowed to move away from.
"There can't be a peaceful society within a capitalist system," student Vicente Moronta told state television.