A woman was shot dead and dozens injured in the Venezuelan capital Caracas on Wednesday, in clashes between opposition supporters and pro-government forces.
Tear gas and water cannon were fired by the military amid rival demonstrations.
Opposition leader Juan Guaidó called for those responsible for the death of a 27-year-old woman to be found.
Meanwhile, Mr Guaidó called for a series of strikes to force President Nicolás Maduro to relinquish power.
He urged public employees to act on Thursday, saying the stoppages would lead to a general strike.
Mr Guaidó in January declared himself Venezuela’s interim leader, and he has been recognised by more than 50 countries including the US, UK and most Latin America nations.
But Mr Maduro – who is backed by Russia, China and the leaders of Venezuela’s military – has refused to cede power.
The president dismissed suggestions he had been ready to flee the country and accused the US of directing an attempted coup. Those involved would be punished, he said.