Venezuelan opposition leader Juan Guaidó has called for an escalating series of strikes to force President Nicolás Maduro to relinquish power.
Mr Guaidó urged public employees to act on Thursday, saying the stoppages would lead to a general strike.
A woman was killed and dozens were injured when protesters and security forces clashed in Caracas on Wednesday.
Mr Maduro meanwhile dismissed suggestions he had been ready to flee and accused the US of directing a coup.
Those involved would be punished, he said.
Tensions over the crisis are also rising between the US and Russia.
US Secretary of State Mike Pompeo said the US could take military action to resolve the crisis and accused Russia and Cuba of destabilising the country through their support for Mr Maduro.
Russian Foreign Minister Sergei Lavrov told Mr Pompeo that America’s influence over Venezuela was destructive and a violation of international law.
Mr Guaidó declared himself Venezuela’s interim leader in January and has been recognised by more than 50 countries, including the US, the UK and most in Latin America.
But Mr Maduro – backed by Russia, China and the top of the country’s military – has refused to cede power.
How significant is Guaidó’s latest move?
In a series of tweets (in Spanish), Mr Guaidó said the final phase of the “Operation Liberty” had begun and it was the turn of public workers to join in.
He urged protesters to stay on the streets until Mr Maduro’s government would be finally forced to resign.
Mr Guaidó has been courting the public sector for weeks – but winning their support will be difficult, the BBC’s Americas editor Candace Piette says.
For years, state employees have been told that if they did not turn up at government rallies they would lose their jobs.
So if the opposition leader does win them over, it will be a huge victory against President Maduro, our editor says.
On Wednesday both pro- and anti-government supporters held large demonstrations.
Both were initially peaceful but there were then reports of gunfire in the city. Later on Wednesday a local NGO, the Venezuelan Observatory of Social Conflict, said a 27-year-old woman had been shot dead during a rally in the opposition stronghold of Altamira.
At least 46 people were injured in the clashes.
How did the ‘attempted coup’ unfold?
On Tuesday Mr Guaidó posted a video showing him with a number of men in military uniform. He said he had the support of “brave soldiers” in Caracas.
He urged Venezuelans to join them in the streets, and appeared alongside another opposition leader, Leopoldo López, who had been under house arrest since 2014.
Supporters on both sides then gathered around Caracas throughout the day, and there were clashes between Mr Guaidó’s supporters and armed military vehicles.
Spain’s government later said that Mr López and his family had sought safety in their embassy, but said the opposition figure has not claimed political asylum.
What other international reaction has there been?
UN Secretary General António Guterres has appealed for both sides to avoid violence, while the EU has called for “utmost restraint to avoid the loss of lives and an escalation in tensions”.
The US has reiterated its support for Mr Guaidó.
Governments who still back Mr Maduro – including Bolivia and Cuba – condemned Mr Guaidó’s efforts as an attempted coup.
The Mexican government expressed “concern about a possible increase in violence” while Colombian President Ivan Duque urged the Venezuelan military to stand “on the right side of history” against Mr Maduro.
An emergency meeting of the Lima Group of Latin American countries has been scheduled for Friday.
