A woman was shot dead and dozens injured in the Venezuelan capital Caracas on Wednesday, in clashes between opposition supporters and pro-government forces.
The military fired tear gas and water cannon amid rival demonstrations.
Opposition leader Juan Guaidó called for those responsible for the death of a 27-year-old woman to be found.
He also urged public employees to go on strike on Thursday, to try to force President Nicolás Maduro to stand down.
In January, Guaidó 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.
As the head of the opposition-controlled National Assembly, he invoked the constitution to assume an interim presidency, arguing that Maduro’s re-election last year was illegitimate.
But 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.