Eighteen militiamen are on trial in the east of the Democratic Republic of Congo on charges of raping 46 children.
Some of the victims from the village of Kavumu were just 18 months old.
The men allegedly targeted young girls between 2013 and 2016 because a spiritual adviser told them that the blood of virgins would grant them supernatural protection.
The alleged militia leader, Frederic Batumike, a provincial legislator, and the other defendants deny the charges.
Rights groups hope the trial will help to end a culture of rape as a tool of war in DR Congo.
"The start of the trial is a strong signal in the fight against impunity," Jean Chrysostome Kijana, an activist representing the victims, told Reuters news agency.
Proceedings started 10 hours late and lasted only 20 minutes on Thursday, during which time the defendants' names were read aloud, according to Reuters.
Advocacy groups have told Reuters that the case has been particularly difficult to investigate because the victims were so young.
"Their families were often asleep when the alleged rapes occurred," Reuters reports.
Villagers believed a magic powder was being used to induce sleep, investigative journalist Lauren Wolfe told BBC Newsday:
"I thought... Could they [the attackers] be using some kind of herbal anaesthetic? It actually turned out to be true. They were."
She said the militiamen had been illegally squatting on an "extremely fertile" plantation previously owned by a German botanist who was murdered in 2012.
Following more than 20 years of conflict, much of eastern DR Congo is under the control of various militia groups.
The Democratic Republic of Congo was labelled "the rape capital of the world" by Margot Wallstrom, the former UN special representative on sexual violence in conflict.
Writing in The Guardian, Wolfe says that two years ago "one UN official resigned out of frustration at the UN's continued failure to halt the atrocities" in Kavumu.