US President Donald Trump has said he recognises Venezuelan opposition leader Juan Guaidó as interim president.
The announcement came minutes after the 35-year-old declared himself acting leader in Caracas on Wednesday.
A number of South American countries, including Brazil, Colombia and Peru, have also recognised Mr Guaidó as Venezuela's legitimate president.
It comes amid mass protests against President Nicolás Maduro who has overseen years of economic freefall.
Hyperinflation, power cuts and shortages of basic items have driven millions of people out of Venezuela.
Mr Maduro was sworn in for a second term earlier this month, after a vote marred by an opposition boycott and widespread claims of vote-rigging.
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In response to Mr Trump's recognition of the opposition leader, Mr Maduro broke diplomatic ties with the US and gave its diplomatic staff 72 hours to leave Venezuela.
He accused Washington of trying to govern Venezuela from afar and said the opposition was seeking to stage a coup.
Some counter-demonstrations are also being held in support of Mr Maduro, but these are reported to be on a much smaller scale.
Earlier on Wednesday, Mr Guaidó told a cheering crowd in Caracas that the protests would continue "until Venezuela is liberated".
Mr Guaidó, who is head of the National Assembly, called on the armed forces - who have so far backed Mr Maduro - to disobey the government.
Secretary of State Mike Pompeo rejected Mr Maduro's move to cut ties with the US, saying that the US did not recognise him as leader and would instead conduct relations "through the government of interim President Guaidó".
Mr Pompeo urged Venezuela's military to support efforts to restore democracy and said the US would back Mr Guaidó in his attempts to establish a government.