Tens of thousands are gathering across Venezuela to march in protest against President Nicolás Maduro.
Four people are said to have died in clashes before the protests, as riot police mobilise to guard demonstrators.
National Assembly president Juan Guaidó, who organised the opposition march, is urging the army to disobey the government.
The US government has signalled its support for Mr Guaidó and called for President Maduro to go.
Early images from Wednesday’s protests show some demonstrators facing off against National Guard security forces in the capital Caracas, and tear gas being fired.
Anti-government protestors have turned up in “many cities” across the country, newspaper Tal Cual reported Wednesday.
Other demonstrations are being held in support of Mr Maduro.
Why are people protesting?
Venezuela has been in economic freefall for a number of years under the leadership of President Maduro.
Hyperinflation and key shortages, including of food, has forced millions out of the country.
Wednesday’s protests were called by Mr Guaidó after the president, who has been in power since 2013, was sworn into office for another six years earlier this month.