Venezuela opposition says government broke election law
The Venezuelan opposition has made an official complaint against the government following allegations that it broke the law by continuing its electoral campaign on state television.
On the eve of the election, acting President Nicolas Maduro appeared on TV visiting the tomb of Hugo Chavez.
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, he 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 recognise identity card numbers and register the vote anonymously.
Polls will open at 06:30 local time (10:30 GMT) and close 10 hours later, although they will stay open until all those queuing at closing time have voted.
The former president died on 5 March, 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 19 April and serve until January 2019, to complete the six-year term that Mr Chavez would have begun in January.
Mr Chavez's handpicked candidate Nicolas Maduro is seen as the front-runner, but recent polls said the gap between him and his rival, Mr Capriles, was narrowing.
Both sides staged massive rallies to mark the official end of their campaigns on Thursday.
But since 2002, Mr Chavez' supporters have staged celebrations on 13 April, the date when the late leader returned to power after a brief coup in 2002.
Venezuelan state television showed Mr Maduro visiting the tomb of the late leader, accompanied by the Argentine football star Diego Maradona, who also took part in Mr Maduro's final rally on Thursday.
"Let's honour his [Mr Chavez's] memory, his legacy," Mr 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.
Mr 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.