OTTAWA -- Three Ottawa-area teenage girls befriended other teens on the Internet through the powerful lure of Facebook and other social media platforms before forcing them to work as "escorts," a court was told Monday.

All three of the accused girls, whose identities are protected under a publication ban, pleaded not guilty to a raft of charges -- which took the court clerk more than 20 minutes to read into the public record.

Some of the alleged victims, ranging in age from 13 to 17, were forced to have sex with "clients" of the accused, beaten, confined and robbed, Crown prosecutor Julien Lalonde told court on the opening day of what is expected to be a month-long trial.

Several of the victims also had their clothes ripped off and were photographed in the nude, prosecutors alleged.

"They were told they would be working as escorts," Lalonde said in his opening remarks.

In one case, a 13-year-old victim was assaulted after her mother dropped her off for what she thought was a sleepover with a friend, said prosecutors.

Court was told the victim's mother immediately called 911 the following morning when her daughter came home and collapsed in tears.

Ever since they first surfaced last year, the stunning allegations have served as a stark reminder to parents to be mindful about the people their teenaged children might be in contact with on platforms like Facebook and Twitter.

As their family members watched from the courtroom's spectator gallery, two of the accused sat in the prisoner box, a city police constable between them.

One of the girls, her brown hair in a ponytail flung over the left shoulder of her dark blazer, frequently looked over so-called "storyboards" used by prosecutors as exhibits in the trial.

The second teen, clad in a white blouse and dark pants, slouched forward during much of the proceedings, looking down and twirling her long, black hair between her fingers.

The third accused, who was not in custody, wore a brightly coloured blouse and a black skirt as she sat among family members in the public gallery.

The storyboards themselves illustrated the Crown's assertions of how teenaged victims were either threatened with violence or physically beaten, and then connected to "johns" who paid to be with young prostitutes.

In one case, a man in his 30s allegedly paid $60 for oral sex with a 16-year-old. In another, court heard how a prospective client declined to have sex with one of the teens after the victim made clear to him that she was with him against her will.

The three accused are facing dozens of charges including human trafficking, procuring for prostitution, abduction and sexual assault.

They also face child pornography charges in connection with the alleged nude photos taken of the victims.

The girls were arrested last June in the Ottawa area after social media was allegedly used to lure seven girls between 13 and 17 years of age to a community housing project in southeast Ottawa.

The victims were allegedly invited to the home where they were held against their will, given alcohol and, in at least one case, drugged.

Two of the accused girls were 15 and the third was 16 at the time of their arrests.

The charges relate to three separate incidents in May and June last year.

A publication ban under the Youth Criminal Justice Act prevents identification of both the accused and their alleged victims.

Lawyers were also expected to argue on Wednesday that reporters be allowed to "tweet" from the courtroom after at least three media outlets complained about a court-imposed ban on the use of cellphone technology during the trial.