Some were released, while 13 appeared on Friday before a tribunal in Rabat that specialises in cases involving terrorism charges, and were detained at a prison near Rabat.
The prosecutor's office confirmed on Tuesday that six of the 13 had been handed over by the Algerian authorities after trying to contact the Salafist Group for Preaching and Combat (GSPC) for military training.
It said that among the 13 was their leader Mustafa al-Khayri. They face charges of threatening public safety, theft, extortion, illegal possession of weapons, formation of a gang to prepare and commit terrorist acts, and membership of an unauthorised association.
The prosecutor's office said they had been indoctrinated by those who preached violence as a way of securing change.
They had already begun to carry out acts of violence on the basis of a belief that authorised illegal acts such as theft and attacks. No trial date has been set, judicial sources said.
The head of the Moroccan Human Rights Association, Abd al-hamid Amin, told reporters on Tuesday that some of those arrested in Tetouan had been tortured.
Amin, in a letter to the Justice Ministry, complained that Moroccan law on detention had not been respected. Some suspects remained in custody nearly three weeks, exceeding the maximum 12 days for detention without charge, he said.
Morocco launched a vast campaign of arrests and trials targeting suspected extremist groups after a wave of attacks in Casablanca in May 2003 claimed 45 lives including those of 12 bombers.