Venezuelan opposition leader Maria Corina Machado addressed a mass rally in the capital, Caracas, defying government calls to arrest her.
Ms Machado went into hiding earlier this week after accusing President Nicolás Maduro of cheating opposition candidate Edmundo González into a clear victory in the presidential election.
The president in turn accused Ms. Machado of stockpiling violence and said she and Mr. Gonzalez should face decades in prison.
The electoral commission, controlled by Mr Maduro’s allies, insists he won last Sunday’s vote with 52% of the vote, but independent observers say it lacks transparency.
The commission has not released a full breakdown of results. The opposition said their own vote counts showed they won the election by a wide margin. Pre-election polls showed a clear victory for the challenger.
On Saturday, Ms. Machado addressed thousands of supporters in Caracas from a truck carrying a “Venezuela Wins” banner.
“We have never been stronger,” she told the crowd, adding, “The regime has never been weaker… It has lost all legitimacy”.
The opposition leader, who was blocked from taking part in the election, has been in hiding for several days.
Earlier this week, Ms. Machado wrote in the Wall Street Journal that she, like other opposition leaders, “feared for her life.”
She was greeted with cheers of “freedom, freedom” and was accompanied by several other opposition leaders except Mr Gonzalez.
In another video, he urged supporters to “respond to the regime’s attacks with hope, harmony and peace.”
Venezuelan security forces have spent the past few days trying to contain mass protests. At least 11 people died in clashes with police.
More than 1,000 opposition demonstrators were arrested.
The government is facing growing international pressure. US Secretary of State Antony Blinken said on Friday there was “overwhelming evidence” that Mr Gonzalez won the election.
His intervention came as the presidents of Brazil, Mexico and Colombia all called on Venezuela to release detailed election results.
Other regional governments, including Argentina, Costa Rica, Panama and Uruguay, have expressed concerns about the vote.
But Maduro has support from allies in Russia, China and Cuba.
He has asked Venezuela’s Supreme Court to review the vote to confirm the result, giving him another six years in power.
The opposition said the court was in the hands of government loyalists and would delay the release of the statistics. Mr. Gonzalez boycotted the court proceedings on Friday.
