Venezuela's electoral authority, blasted by critics as favouring the ruling socialists, proclaimed Maduro the winner in last Sunday's vote, saying on Monday he obtained 51 per cent compared to 46 per cent for opposition candidate Edmundo Gonzalez. The authority reaffirmed a similar margin on Friday.
The published election result sparked widespread allegations of fraud and protests. Subsequently security forces cracked down on protests which Maduro's government labelled part of an attempted US-backed coup.
Some 1200 people have been arrested in connection with the demonstrations in Venezuela. (AP PHOTO)
"This time there will be no forgiveness," Maduro told supporters at a rally in Caracas, where he said some 2000 people had been detained in connection to "crimes" during the protests. He pledged "maximum punishment".
Maduro's supporters says they are defending democracy.
"Today we are here heeding the call of our president … to defend democracy," Alfredo Valera, president of Venezuela's Fontur union, who took part in a pro-government caravan in Caracas, told state television.
Elsewhere, opposition supporters marched to demand justice, buoyed by the presence of leader Maria Corina Machado, who emerged from hiding on Saturday to join her demonstrations on the streets of Caracas.
"Just as it took us a long time to achieve electoral victory, now comes a stage that we take day by day, but we have never been as strong as today, never," Machado told supporters in Caracas.
Supporters were happy to see Machado in the streets after the leader said in a Thursday op-ed for the Wall Street Journal that she was in hiding and feared for her life.
In addition to Caracas, demonstrations took place in cities including Valencia, Maracaibo and San Cristobal.
"I don't deny it's a little scary to see security forces pass by," said vendor Maria Luzardo, 46, in San Cristobal.
"If (Machado) is brave enough to be on the streets despite the threats, so are we. Venezuela is calling us."
So far, at least 20 people have been killed in post-election protests, according to advocacy groups, including US-based Human Rights Watch.
Some 1200 others have been arrested in connection with the demonstrations, according to the government.
During the week, some Venezuelans have appeared outside police stations seeking news of their detained family members.
The Organization of American States urged peace in Venezuela ahead of the planned demonstrations.
"Today we urge that there not be one more political prisoner, nor one more tortured person, nor one more disappeared person, nor one more murdered person," said the OAS, which this week called the election results unreliable.
Nations including the US and Argentina have already recognized Gonzalez as the election's winner, with US Secretary of State Antony Blinken on Thursday citing "overwhelming evidence".
