Hundreds of thousands of Venezuelans are gathering today against President Nicolas Maduro, while the US considers recognising opposition leader Juan Guaido as the country's leader.
The rally in Caracas followed dozens of violent protests and looting overnight that left four people dead, according to an official and a rights group.
The opposition has been emboldened by young Congress chief Juan Guaido, who has led a campaign to declare Maduro a usurper and has promised a transition to a new government in a nation suffering a hyperinflationary economic collapse.
Mr Maduro was inaugurated on 10 January to another term in office following a boycotted election last year.
Putting more pressure on the socialist leader, sources said the Trump administration told US energy companies it could impose sanctions on Venezuelan oil as soon as this week.
Any change in government in Venezuela will rest on a shift in allegiance within the armed forces. They have stood by Maduro through two waves of street protests.
"We've come out to support the opposition and preserve the future of my son and my family, because we're going hungry," said Jose Barrientos, 31, an auto parts salesman in the poor west end of Caracas, who joined yesterday's protest that he said was met with tear gas and police gun fire.
Demonstrators clogged avenues of eastern Caracas, a traditional opposition bastion, where Guaido was expected to speak.
US President Donald Trump could recognise Mr Guaido as the legitimate president as soon as today, according to two people familiar with the matter.
The ruling Socialist Party, which says the country is victim of an economic war by the United States, is holding a rival march.
"I'm here to defend the fatherland, to defend Venezuela and our president - I'm sick of (the opposition) saying that they're firing him," said Yenny Duarte, 46, a member of the country's civilian military, who was marching in support of Maduro.
Guaido urges military coup
Mr Guaido, 35, has called for the military to disavow Maduro and promised amnesty for those who help to bring about a return to democracy. He has said he would be willing to replace Maduro as interim president with the support of the military and to call free elections.
"To all of the national armed forces, our call is clear - from this parliament, we extend our hand and ask that you come to the side of the constitution and the people, your people," Mr Guaido wrote on Twitter.
A 16-year-old was shot to death at a protest on Tuesday in wester Caracas, according to rights group Venezuelan Observatory of Social Conflict.
Three people were shot dead yesterday in southern Bolivar City during a looting of a grocery store that followed a nearby protest, Bolivar state governor Justo Noguera said in a telephone interview.