Venezuelan leader Nicolás Maduro has broken off relations with the US after it recognised opposition leader Juan Guaidó as interim president.
Mr Maduro gave US diplomats 72 hours to leave the country.
On Wednesday Mr Guaidó declared himself president during mass protests. The US said "former President Maduro" no longer had authority and urged the army to back Mr Guaidó instead.
So far the army has remained loyal to Mr Maduro.
Venezuela has been in economic freefall under President Maduro. Hyperinflation, power cuts and shortages of basic items have driven millions of people from the country.
What happened at the Caracas protest?
Thousands of Venezuelans attended a rally on Wednesday in support of Mr Guaidó, who is the head of the National Assembly.
He told the cheering crowd that protests would continue "until Venezuela is liberated".
Mr Guaidó then raised his right hand and said: "I swear to formally assume the national executive powers as acting president," vowing to lead a transitional government and hold free elections.
He called on the armed forces – who have so far backed Mr Maduro – to disobey the government.
Venezuelan NGOs said that 14 people were shot dead during protests on Tuesday and Wednesday.
How did the US respond?
President Donald Trump recognised Mr Guaidó as interim president in an apparently co-ordinated move minutes after the 35-year-old declared himself acting leader.
In a statement, he described Mr Maduro's leadership as "illegitimate", adding: "The people of Venezuela have courageously spoken out against Maduro and his regime and demanded freedom and the rule of law."
It warned Mr Maduro not to threaten the safety of the Venezuelan people and said tougher sanctions could be imposed.
Mr Trump told journalists he was not considering military action but added that "all options are on the table".
He called on other nations to follow suit in supporting Mr Guaidó./