Politicians critical of Chavez criticised the country's high crime rates and electricity rationing ordered by the government in response to an energy crisis stemming from a drought that drained the country's dams, as well as currency devaluation.
The marches were the first since Chavez sharply devalued the bolivar currency and deployed soldiers to stop retailers hiking prices.
Thousands of government supporters also poured into western Caracas to hear a speech delivered by Chavez in which he told followers he embodied the heart and soul of the Venezuelan people.
|Chavez urged Venezuelans to 'continue building a new socialist state' [AFP]
"I demand absolute loyalty to my leadership... anything else is betrayal," Chavez said.
"I am not an individual, I am the people. It's my duty to demand respect for the people.
"Let's expand our socialist project," he said.
One supporter said he "came from far away to be here, to defend the revolution and the movement led by commander Hugo Chavez".
"Things aren't all as we would like them to be, but we know that El Comandante is doing what he can to help us, the poor,'' Yorbert Rodriguez, a 39-year-old bricklayer, said.
Over 5,000 police and national guard troops were deployed along march routes to prevent clashes between rivals. There were no reports of arrests or violence, which has marred numerous political rallies in the past.
Venezuela will hold elections in September in which Chavez hopes to secure at least two thirds of seats to maintain his current legislative majority.
According to opinion polls, the popularity of the leftest leader, which approached 60 per cent approval at the beginning of 2009, has reduced to less than 50 per cent.
Chavez, a vocal opposer of US influence in the region, has held onto power since 1999 and remains popular, especially among the country's poor majority.