The regional elections held Sunday had 23 gubernatorial seats up for grabs. It was the first major election since July's controversial and deadly
vote for a constituent assembly, and is also the country's first contested election since December of 2015.
With 95.8% of the votes counted, Venezuela's National Electoral Council said that Máduro's party was favored in 17 states and the opposition coalition Mesa de la Unidad Democrática (MUD) in five. The outcome in the remaining state was not yet clear, it said in a statement.
Máduro called Sunday's vote "a success for Venezuela and the revolutionary democracy, for the socialist democracy."
But opposition politician Gerardo Blyde early Monday demanded a complete audit on all of Sunday's results.
Blyde, a campaign coordinator of the opposition coalition MUD, has called for street protests later Monday.
Before the vote, government loyalists held all but three governorships, but observers had said there was a chance for the opposition to make gains.
"If the vote were to be completely free and fair, the (opposition) would likely win between 18 and 21 states," according to a pre-election analysis by the Eurasia Group, a political risk research and consulting firm.
In the lead-up to election day, the opposition accused electoral authorities of making the ballots confusing and moving polling locations in opposition strongholds in an effort to boost pro-government candidates.
The US State Department condemned Venezuela's National Electoral Council last week, saying its actions call into question "the fairness of the electoral process."
The Venezuelan Electoral Council called the US statement an "aggression perpetrated against our sovereignty," and said changes were made for security reasons.
Concerns that the Electoral Council's changes would sow confusion appeared to have come to fruition Sunday, with many voters unsure about where they were supposed to vote. Long, slow-moving lines greeted voters at polling stations.
Ludmilla Velez Lascar said she was determined to cast her ballot despite her polling location being changed. "Maybe they don't want my vote," Velez Lascar said. "But we have to vote. We have to elect ... our governors."
Last election erupted in violence
Venezuelans headed to the polls Sunday less than three months since the last major vote, when violent clashes erupted between protesters and police, leaving at least six people dead. More than 120 people were killed in months of protest leading up to that vote, the Venezuelan attorney general's office said.
The vote allowed Máduro to establish a new institution called the Constituent Assembly, which was stacked with his supporters. It replaced the National Assembly, which had been controlled by Maduro's opponents.
The new Constituent Assembly gave Máduro the power to rewrite Venezuela's constitution.
In wake of the election, London-based Smartmatic -- which provided the voting technology -- said turnout figures were manipulated
The US Treasury Department called the July election "illegitimate" and slapped new sanctions