CARACAS: Venezuela's opposition holds an unofficial referendum on Sunday to increase pressure on President Nicolas Maduro as he seeks to create a legislative superbody that his adversaries call the consolidation of a dictatorship.

The symbolic poll, which will also ask voters if they want early elections, is intended to further dent Maduro's legitimacy amid a crippling economic crisis and three months of anti-government protests that have led to nearly 100 deaths.

The opposition has cast the vote, which begins at 7 a.m. local time at some 2,000 centers around the country, as an act of civil disobedience to be followed by "zero hour," a possible reference to a national strike or other escalated actions against Maduro.

But the vote does not appear to augur a short-term change of government or a solution to the country's political stalemate.

Maduro, 54, says Sunday's plebiscite is illegal and meaningless. Instead, the leftist leader is campaigning for an official July 30 vote for the new assembly, which will be able to rewrite the constitution and dissolve state institutions.

"(Even with) rain, thunder or lightning, Sunday's poll will go ahead!" said opposition leader Henrique Capriles in a Friday evening broadcast. "We Venezuelans are going out to vote for the future, the fatherland and the freedom of Venezuela."

Voters will be asked three questions: if they reject the constitutional assembly, if they want the armed forces to defend the existing constitution and if they want elections before Maduro's term in office ends in 2018.

Some public employees, under government pressure not to participate in opposition events, are seeking creative ways to vote in the plebiscite without being noticed.