In the western state of Tachira, two teenagers, aged 17 and 13, were also killed. The first, Luis Ortiz, was killed in the municipality of Cardenas, when armed groups allegedly fired at the protesters.

The 13-year-old, who was unnamed by authorities, was reported killed in the town of Capacho Viejo.

Polls opened at 6 am for elections to choose the members of a National Constituent Assembly (ANC) to debate and amend the Constitution, an initiative proposed by the government of President Nicolas Maduro to resolve the political crisis and rejected by the opposition as an attempt to consolidate his power.

Caracas-based news network Telesur posted photos on its website that showed large crowds or long lines at polling stations in different parts of the country.

The coalition of conservative opposition parties, known by its Spanish acronym MUD, contested reports that turnout was robust, posting images of abandoned streets outside what it alleged were polling stations on Sunday.

Despite the opposition calling on its supporters to defy a ban against anti-government demonstrations, there were no reports of major disturbances, according to electoral officials.

While governments such as the US, Mexico, Colombia and Panama have said they would not recognize the results of the election, Venezuelan authorities were defiant.

The President of Venezuela's Constituent Commission, Elias Jaua, said that the ANC did not need the recognition of "any government."

After voting around midday, Jaua told the press that "the ANC is a constitutional instrument, no government of the world has the right to recognize or not the will of the Venezuelan people."

He took particular aim at the US and Colombia saying that Juan Manuel Santos, president of Colombia, and Donald Trump, president of the United states, "must respect it, as this people has its own soul and conscience."

"Tomorrow (Monday), we will start the ANC and, through it, the path to recovering the guarantees of peace and dialogue among all Venezuelans....hopefully the opposition understands this," he concluded.