The families were planning to submit a letter of complaint to the justice minister to draw his attention to what they said was the miserable condition of prisoners at the Sala detention centre who have been on hunger strike for three weeks now.
Aljazeera's correspondent in Morocco, Hasan al-Fatih, was beaten up by Moroccan security forces when Aljazeera's TV crew tried to prevent them from smashing their camera in a bid to stop them from reporting on the protest.
Speaking from Rabat on Thursday, al-Fatih said: "We were covering a sit-in organised by families of detainees of al-Salafiya al-Jihadiya group in front of the headquarters of the Moroccan justice ministry.
"At first, the Moroccan security authorities asked us to leave the area without assigning any reason.
"When we insisted on filming the protest, some security personnel intervened, particularly the support forces, which troubled us a lot."
Al-Fatih said: "One member of the general information force tried to smash an Aljazeera camera but we prevented him from doing so. Other members of the force responded to our action in a violent manner, and I was beaten on the neck and my shirt was torn. I am still in pain from the bruises on my neck."
He said other security officers then intervened to disperse the general information personnel who had prevented us from covering the protest.
Earlier, agencies reported that Moroccan police rounded up 88 members of the country's main Islamic opposition as part of a crackdown to limit the unauthorised movement's influence.
"The authorities want to limit the group's activities, not destroy it"
Hassan II University,
Group members on Wednesday said security forces arrested more than 500 members of Al Adl wa al Ihsane (Justice and Charity) since late May after it launched an "open doors" campaign to recruit outside traditional areas such as mosques and universities.
Some were beaten and nearly all were quickly released.
Fathallah Arslane, Al Adl's spokesman, told Reuters that 45 group activists were arrested in the town of Bouarfa in northeast Morocco on Tuesday night before being set free in the early hours of the morning.
He said 43 Al Adl members were rounded up earlier in Oujda and Nador, also in the northeast, among them the group's second-in-command, Mohamed Abadi.
All but one were released, although Abadi and two others must face prosecutors at the end of the month.
Mohamed Darif, an Islamism specialist at Hassan II Uuniversity in Mohammedia near Casablanca, said: "The authorities want to limit the group's activities, not destroy it."
For his part, Arslane says: "The authorities want to muzzle us."
Al Adl's founder, Abdessalam Yassine, was under house arrest for almost 10 years until 2000 for challenging the monarchy's powers, including the king's status as Commander of the Faithful - the spiritual leader of the country's Muslim community.
The group, Morocco's biggest opposition force with about 250,000 members, would like to see an Islamic state organised according to Sharia law, although it says it rejects violence.