The former Spanish prime minister has urged the defeated opposition candidates in Sunday's Venezuelan presidential elections to lodge their complaints through the appropriate channels.

Incumbent president Nicolas Maduro won re-election until 2025 after a poll with a record low voter turnout and in which opposition candidates have denounced numerous irregularities.

"They have every right to present any challenge to the facts on the table. It is part of the democratic practice and this challenge will have to go through existing channels" in the National Electoral Council (CNE), former Spanish prime minister and mediator in the Venezuelan elections, Jose Luis Rodriguez Zapatero, said in an exclusive interview with EFE.

Zapatero looked beyond the expected results dispute and pointed out that the hard work to overcome the political chasm that has divided the country in recent years needed to start immediately.

There was a pressing need for dialogue as "peace comes above all else in any situation", the mediator said.

Former governor Henri Falcon and the evangelical pastor Javier Bertucci, the two main candidates who lost to Maduro, said that there were more than 1,000 irregularities and called for new elections.

"To Henri Falcon, to Javier Bertucci... to all the leaders of the opposition, let's have a meeting. Let's meet and talk about Venezuela," Maduro said at Miraflores Palace, in front of hundreds of supporters.

Maduro has ruled the South American nation since the death of his predecessor Hugo Chavez in 2013.