Deadly protests rocked Venezuela on Sunday as voters broadly boycotted an election for a constitutional superbody that unpopular leftist President Nicolas Maduro vowed would begin a "new era of combat" in the crisis-stricken nation.

Opposition parties are sitting out what they call a rigged election aimed at consolidating Maduro's power, leaving streets deserted and polling stations largely empty and dealing a blow to the legitimacy of the vote.

Anti-Maduro activists wearing hoods or masks erected barricades on roads and scuffles broke out with security forces who moved in quickly to disperse the demonstrators. Authorities said seven people were killed in the unrest and the opposition said the true death toll was around a dozen people, which would make Sunday one of the deadliest days since massive and sustained protests kicked off in early April.