Nicaragua's Vice President Rosario Murillo has called protestors against new pension reform "vampires demanding blood".
Two protestors and a policeman were killed in the capital, Managua, after demonstrations turned violent.
The protests continued for a third day as anti-riot police used tear gas to break up the demonstrations.
The wave of unrest is the biggest since President Daniel Ortega took power in 2007.
The protests followed the introduction earlier this week of new legislation that increased worker and employer pension contributions and reduced overall pension payments by 5%.
Hundreds of pensioners reacted by taking to the streets on Wednesday.
They were joined the next day by thousands of students and workers in cities across Nicaragua.
Vice President and First Lady Rosario Murillo appeared to be managing the government's emergency response with little sign of her husband, President Daniel Ortega, in public.
She compared the protestors to "vampires demanding blood to feed their political agenda".
But protestors complained in various cities that riot police attacked the demonstrators and that the government had been sending in its supporter groups known as "colectivos" to beat them up.
Four independent television networks accused the government of taking them off-air after they broadcast the demonstrations live.
A spokeswoman for the UN's High Commissioner for Human Rights, Liz Throssell, urged the government to prevent further attacks on demonstrators and the media.
She also urged the protesters to demonstrate "peacefully".