Venezuelan opposition leader Maria Corina Machado has emerged from hiding to join her supporters protesting in the streets of Caracas against contested national election results, as demonstrators marched across the country.

Thousands of people rallied in Venezuela’s capital on Saturday, waving the national flag and singing the national anthem in support of the opposition leader, who they believe won the presidential election by a landslide.

“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.

Venezuela’s electoral authority, blasted by critics as favouring the governing party, proclaimed President Nicolas Maduro the winner in last Sunday’s vote, saying on Monday he obtained 51 percent compared with 46 percent for opposition candidate Edmundo Gonzalez. The authority reaffirmed a similar margin on Friday.

The published election result has prompted widespread allegations of fraud and protests.

On Saturday, supporters chanted and sang as Machado arrived at the rally in Caracas, happy to see her 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.

Ecstatic, they crushed around her as she climbed onto a raised platform on a truck to address the crowd.

“I am happy because I am here with Maria Corina, supporting Venezuela to escape this terrible injustice,” Yamilet Rondon, 42, who was waving a Venezuelan flag, told Reuters.

In addition to Caracas, demonstrations took place in cities including Valencia, Maracaibo and San Cristobal.

“I came to this march with some fear, with fear of the repression we’ve seen, but it is our struggle,” preschool teacher Susana Martinez, 42, said at a demonstration backing the opposition in Valencia.

Meanwhile, Maduro urged his backers to attend his own “mother of all marches” elsewhere in Caracas.

“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.

Maduro’s government has cracked down on opposition protests and labelled them as part of an attempted US-backed coup.

Security forces have arrested hundreds of opposition supporters who have taken to the streets in the days after the disputed poll.

So far, at least 20 people have been killed in post-election protests, according to rights group Human Rights Watch.

Earlier, the Organization of American States called for calm.

“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 recognised Gonzalez as the election’s winner, with US Secretary of State Antony Blinken on Thursday citing “overwhelming evidence.”

Costa Rica, Ecuador, Panama and Uruguay also concluded on Friday that Gonzalez received the most votes.

Meanwhile, countries including Russia, China and Cuba, have congratulated Maduro.