Venezuelans are expected to gather for mass protests on Wednesday after opposition leader Juan Guaidó called for fresh demonstrations.
It comes the day after President Nicolás Maduro said he had stopped an "attempted coup" by the opposition.
"Today we continue," Mr Guaidó tweeted. "We will keep going with more strength than ever, Venezuela."
Mr Guaidó says the armed forces now back the protesters, but Mr Maduro says they have not turned against him.
In a fiery television address on Tuesday, Mr Maduro accused protesters of "serious crimes" which he said would "not go unpunished", and said the US was plotting against him.
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 leadership to his rival.
US Secretary of State Mike Pompeo said military action was "possible" if necessary but that the US would prefer a peaceful transition of power.
What's the latest?
Early on Wednesday Mr Guaidó retweeted a list of planned protest points in the capital, Caracas.
Demonstrators planned to gather at these locations at 10:00 local time (14:00 GMT). May Day is a public holiday in Venezuela.
Student and opposition groups have tweeted images of protesters massing in the streets amid reports of a large police presence.
What happened 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 has 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 confirmed that Mr López and his family had sought safety in their embassy, but said the opposition figure has not claimed political asylum.
Chilean foreign minister Roberto Ampuero confirmed on Twitter he had initially come to their embassy but later transferred to Spain's.
Source: bbc