Supporters of Venezuela’s self-declared interim president Juan Guaidó are gathering for nationwide demonstrations.
Saturday’s protests are intended to ramp up pressure on President Nicolás Maduro to step down and call a snap presidential election.
Mr Guaidó declared himself president last month and was immediately recognised by the US and several Latin American countries.
Russia and China back President Maduro.
Major European countries have given him until Sunday to announce a fresh vote before they join the nations recognising Mr Guaidó as Venezuela’s interim president.
Military support is seen as crucial to Mr Maduro’s hold on power.
TV pictures show crowds gathering in Caracas, Maracaibo, Valencia and Puerto Ordaz.
Both Mr Maduro and Mr Guaidó have taken to Twitter to rally their base.
Mr Maduro used religious imagery to call on supporters to remain strong “in the face of difficulties”. Mr Guaidó called on protesters to show their “gratitude” for international backing, using the hashtag #ElMundoEstáConVzla (TheWorldisWithVenezuela).
A high-ranking Air Force general announced his support for Mr Guaidó in a video message posted online.
Gen Francisco Yanez, the force’s head of strategic planning, called on other members of the military to join him in defecting. It is not clear when or where the message was recorded.
In response, the Air Force’s high command accused him of treason.
Mr Guaidó, meanwhile, says he has held secret meetings with the military to win support for ousting Mr Maduro.