The central question before voters concerned Maduro's intention to hold an election on July 30 to choose 545 members of a citizens' body called the "Constituent Assembly" that would redo the constitution.
Colombia has dealt with rising tensions and a growing number of people crossing the border from Venezuela as the crisis in the oil-rich country has deepened.
Venezuela saw its feuding political factions - the government and the opposition - both prepare their own polls on Sunday to challenge the legimacy of each other's survey of public opinions on the creation of a National Constituent Assembly (ANC).
The opposition also said the country's National Assembly, which it controls, would name new members to the government-dominated Supreme Court, setting up a showdown with President Nicolas Maduro, whose party controls almost all other state institutions.
The opposition blamed a "paramilitary" gang for the shooting, which prosecutors said they would investigate.
China's economy grows 6.9 per cent in second quarter, beating market expectations
Natural gas production increased 8% from a year earlier to 74.1-billion cubic metres for the January-June period, the data showed. But what counts in the overall economy is not the value of the exports but whether the trade surplus narrows or widens.
"I'm calling on the Opposition to return to peace, to respect for the Constitution, to sit and talk", he said on television.
Venezuelans across the world and here in the Valley gathered to vote in an unofficial election.
The latest fatality came on Sunday when gunmen shot a 61-year-old woman in a crowd of opposition voters in the poor Caracas neighbourhood of Catia.
For the past several months, Venezuelans have taken to the streets in opposition of President Maduro.
Maduro and the military dominate most state institutions, but the opposition controls the congress and holds three of 23 governorships.
Iran Calls for US Study on Washington's Record in Implementing JCPOA
Iran's Foreign Minister Mohammad Javad Zarif suggested the USA to reconsider its policy towards the landmark nuclear deal. The negotiations are aimed at bringing an end to the foreign-backed militancy in Syria, which began in March 2011.
When asked if the European Union will explore sanctions against Venezuelan leaders, Mogherini echoed the Spanish foreign affairs minister that defended "specific" and "selective" sanctions against "individual" leaders in Venezuela if the elections to the Constituent Assembly are held.
Fox said he left Venezuela as planned Monday and hadn't been personally notified of any action by the Venezuelan government.
The MUD sees establishment of the ANC, which will rewrite the Constitution, as a power grab by President Nicolas Maduro. The court nullified eight of the assembly's laws between January and October 2016, after making just one such ruling in the previous 200 years, legal experts say.
State media largely ignored Sunday's event, concentrating instead on a simultaneous, government-organised practice run for the July 30 vote. They also voted for the armed forces to defend the current constitution.
Opponents of Venezuela's government blame it for turning one of the region's most prosperous countries into an economic basket case with a shrinking economy, soaring inflation and widespread shortages.
Martin Landau, Oscar victor and 'Mission: Impossible' star, dies at 89
Born into a Jewish family in New York City in 1928, Landau found work at age 17 as a cartoonist for the New York Daily News . In a 2016 interview with The Washington Times, Landau explained what he thought of acting in the 21st century.
The so-called plebiscite was organized outside the formal electoral system, so its results were rejected in advance by the government, which faces a wave of protests that continues after over 100 days and has left nearly a hundred dead. However the vote, dismissed by Mr Maduro as illegal, was largely boycotted by government supporters.
- Police Release Sketch Of Murder Suspect
- Indian Presidential election 2017: All you need to know
- Neerja named the best picture at IIFA 2017
- Lea Michele remembers Cory Monteith four years after his death
- Stressed Froome survives in yellow as Mollema wins stage
- Amazon could be working on a messaging app
- Customers react to bridal store's sudden closure
- Russian Federation vows to boot USA diplomats if compounds aren't reopened
- Kylie Jenner Reveals Sneak Peak of Collaboration With Robert Kardashian
- 'Planet of the Apes' wins box office war with 'Spider-Man: Homecoming'