At least 558 people are being held as political prisoners in Nicaragua for participating in protests against President Daniel Ortega, the Civic Alliance for Justice and Democracy said Wednesday.

The number of detainees is more than double the number acknowledged by the government, which classifies them as terrorists and "coup-mongers."

The prisoners remain "illegally detained" in police lockups and in maximum-security prisons, according to the Alliance.

Among the prisoners are 512 men, 36 of whom have been found guilty of terrorism and other offenses, and 46 women, of whom five have been found guilty of crimes, the Alliance said.

"The situation of insecurity and lack of peace in the country is graphically shown with the number of people imprisoned for exercising their right to protest," the Alianza's Azahalea Solis told reporters upon presenting the figures.

Humanitarian organizations say that the crisis in Nicaragua has resulted in between 325 and 528 dead since it erupted in April, although the government says that 199 people have died.

The Office of the United Nations High Commissioner for Human Rights and the Inter-American Commission on Human Rights have blamed the government for "more than 300 deaths."

Ortega denies the accusations and says that the wave of protests constitutes an attempted coup d'etat.

The protests began on April 18 over a few quickly rescinded changes to the pension system but morphed into the demand for the resignation of Ortega, who was re-elected in 2016 with more than 70 percent of the vote.