With Venezuelans suffering from high inflation, food shortages and soaring crime rates, plus a deepening corruption scandal, the Venezuelan opposition has mounted near-daily anti-government protests since April 1.
The protests have left 66 dead and more than a thousand injured, according to prosecutors.
The unrest has been further fueled by President Nicolas Maduro's call on May 1 for a constituent assembly, which his political opponents say represents a desperate bid to cling to power.
He has proposed July 30 as the day for voting to form the assembly; opponents insist the constitution can be changed only by a referendum.
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"There is no worse way to violate the Constitution than to make a constituent assembly by usurping the power of the people," opposition lawmaker Tomas Guanipa told reporters during Saturday's demonstrations.
Demonstrators are expected to proceed Saturday to Victoria Avenue, in the west of Caracas, where anti-riot forces broke up an early rally with tear gas.
A similar incident occurred in the center of the city, where the presidential palace of Miraflores and the main public offices are located.
The demonstrations came a day after opposition lawmakers filed fresh court cases against Maduro's planned reforms.
That move followed Attorney General Luisa Ortega's separate challenge in the Supreme Court against the president's efforts, in a sign of division within the government camp.
Ortega is the highest-profile official to defy him in the crisis.
German Chancellor Angela Merkel said Friday she was "deeply concerned" by the situation in Venezuela.
"The only thing we can do is encourage dialogue, have some influence -- but for the people in Venezuela the situation is truly very difficult and the solution is not easy," she said during a visit to Mexico City.