Outrage was sparked in Morocco after King Mohamed VI pardoned a convicted Spanish paedophile, who allegedly raped children as young as three.
Several campaign groups called for demonstrations in Rabat to protest the release of 64-year-old Daniel Fino Galvan.
"The king's pardon is a second rape for the victims," Twitter user Meryem El said wrote.
More than 20,000 people subscribed to an online petition describing the decision as an "alarming scandal for Moroccan justice", and urged protesters to stage a sit-in in front of the parliament.
Galvan was sentenced to 30 years in jail in 2011 by a court in the city of Kenitra 40km north of Rabat.
The accused, a former university professor allegedly raped and filmed 11 children aged between 3 and 15.
He reportedly abused his friendship with neighbours who entrusted him with organising birthday parties for their children.
Galvan was one of 48 Spaniards serving time in the North African country who were freed on the request of Spain's King Juan Carlos.
According to Spanish newspaper El Pais, Juan Carlos asked his Moroccan counterpart to free another Spanish convict suffering from health problems during an official visit to the in July.
Juan Carlos also reportedly asked Mohamed VI to be magnanimous with Spaniards serving time in Moroccan jails on the 14th anniversary of his coronation on July 30. In Morocco it is a tradition for the monarch to pardon prisoners on 'Throne Day'. More than 1,000 convicts were freed along with Galvan.
According to Galvan's lawyer, his client was surprised to find his name on the list of those pardoned, since he was supposed to serve another 28 years.
Moroccan authorities confirmed Galvan had been freed and will be expelled from Morocco.
"You can't appeal a royal pardon," Hamid Krayri, a lawyer for some of the victims, told El Pais.