Members of the Venezuelan opposition have made an official complaint against the government following allegations that it broke the law by continuing its electoral campaign on state television.
Venezuela’s acting President Nicolas Maduro appeared on TV visiting the tomb of Hugo Chavez on the eve of the election.
The opposition candidate Henrique Capriles said his opponent was “violating all the electoral norms”.
On Saturday, he launched an internet channel to broadcast his own campaign.
Despite this, Henrique Capriles said he had been “respecting the electoral rules, but those in power don’t know anything other than the abuse of power”.
Almost 19 million Venezuelans will have the right to vote on Sunday for a successor to Hugo Chavez.
Voting will be electronic – one machine will identify voters’ fingerprints, and a second will recognize identity card numbers and register the vote anonymously.
Polls will open at 06:30 local time and close 10 hours later, although they will stay open until all those queuing at closing time have voted.
Venezuela’s President Hugo Chavez died on March 5, after a two-year long battle against an undisclosed type of cancer, prompting a short electoral campaign period before Sunday’s elections.
The winner is due to be sworn in on April 19 and serve until January 2019, to complete the six-year term that Hugo Chavez would have begun in January.
Hugo Chavez’s handpicked candidate Nicolas Maduro is seen as the front-runner, but recent polls said the gap between him and his rival, Henrique Capriles, was narrowing.
Both sides staged massive rallies to mark the official end of their campaigns on Thursday.
But since 2002, Hugo Chavez’ supporters have staged celebrations on April 13, the date when the late leader returned to power after a brief coup in 2002.
Venezuelan state television showed Nicolas Maduro visiting the tomb of the late leader, accompanied by the Argentine football star Diego Maradona, who also took part in Maduro’s final rally on Thursday.
“Let’s honor his [Hugo Chavez’s] memory, his legacy,” Nicolas Maduro told Venezuelans in a speech at the tomb.
An interview with the acting president about the short-lived 2002 coup was also broadcast.
On Friday, members of the opposition campaign said they had lodged an official complaint with the Electoral Commission.
Henrique Capriles also complained on Twitter, saying VTV was “shamelessly breaking the electoral rules”.
For his part, Nicolas Maduro said on the micro-blogging site that there was an alleged “dirty war” being plotted against him from Colombia’s capital, Bogota.