US President Donald Trump has said he recognises Venezuelan opposition leader Juan Guaidó as interim president.
Tens of thousands of Venezuelans are taking to the streets in protest against President Nicolás Maduro.
Mr Guaidó, who called for the demonstrations, declared himself acting leader in Caracas on Wednesday.
Mr Maduro was sworn in for a second term earlier this month, amid widespread allegations of vote-rigging.
Venezuela has been in economic freefall for a number of years under his leadership.
Hyperinflation and key shortages, including of food, has forced millions out of the country.
Early images from Wednesday’s protests showed some demonstrators facing off against National Guard security forces in the capital.
Mr Guaidó, who is head of the country’s National Assembly, has called on armed forces to disobey the government.