At an open air rally before thousands of supporters in red t-shirts, Maduro signed a document yesterday formally establishing the terms for electing members of a "constituent assembly" that will be tasked with drafting a new constitution.
His backers waved red, yellow and blue national flags in defiance of angry opposition protests after the death toll from weeks of clashes reached 53.
But the opposition-controlled National Assembly promptly rejected Maduro's plan.
A man was doused in fuel and set alight on Sunday at a demo. Three people were shot dead late Monday in riots in the western state of Barinas.
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The government and opposition accuse each other of sending armed groups to sow violence during demonstrations.
Maduro has accused the opposition of "terrorism," and is resisting their calls for a vote on removing him from power.
The opposition blames him for an economic crisis that has caused shortages of food and medicine.
It says he plans to pack the "constituent assembly" with his supporters.
In a move set to further inflame the opposition, Maduro said the constitutional body would sit in the chamber of the National Assembly legislature -- the only state institution nominally controlled by his opponents.
"What Nicolas Maduro has announced is nothing but a continuation of a coup against the constitution," said the opposition speaker of the legislature, Julio Borges.
"This National Assembly calls on Venezuelans to continue peaceful protests morning, noon and night in all corners of Venezuela until the constitution is respected."
A total of 53 people have been killed during demonstrations, many of them shot, public prosecutors said yesterday. Looting has broken out in various cities.
A man was set alight on Sunday by a crowd who accused him of thieving. Maduro said he was targeted for being a government supporter.
Fresh riots broke out on Monday evening in the capital and Barinas.
"Venezuelans awake today in mourning for those murdered in our beloved Barinas. Such viciousness against our people!" opposition leader Henrique Capriles wrote on Twitter.