"This is a battle of resistance. We will see who gets tired first: us of fighting, or them of repressing us," said the deputy speaker of the opposition-majority congress, Freddy Guevara.
Several hundred demonstrators gathered in eastern Caracas for the protest march, whose destination was not announced.
Previous attempts to march on the city center have triggered clashes with the security forces.
The streets of Caracas and several other Venezuelan cities have been the scene of running clashes in recent days, with police firing tear gas, rubber bullets and water cannon as demonstrators hurled rocks and Molotov cocktails.
One protester was killed on Thursday. Dozens of people were wounded or arrested.
Maduro is fighting efforts to force him from power over an economic crisis marked by severe shortages and the world's highest inflation.
His popularity, already pummeled by the three-year recession, sank further last week when he and his allies sought to tighten their grip with two Supreme Court rulings that stripped the legislature's power.
The court later reversed the rulings amid an outcry. But the crisis only deepened Friday when authorities banned senior opposition figure Henrique Capriles from holding public office.
That blocks Capriles, who narrowly lost the 2013 presidential election to Maduro, from running against him next year.
The opposition is planning what Guevara called the "mother of all protest marches" on April 19 against Maduro.
The president was meanwhile in Havana for a meeting of foreign ministers from the Bolivarian Alliance for the Peoples of Our America (ALBA), a leftist Latin American bloc co-founded by Maduro's late mentor, Hugo Chavez.
Bolivia, Cuba, Ecuador, Nicaragua and several Caribbean countries are expected to issue a statement of support for Maduro at the meeting.
But the group's influence has waned along with that of Venezuela, a once-booming oil giant devastated by the drop in global crude prices since 2014.