Prosecutors told the court that they would present the "double face" of the accused, Thomas Lubanga, revealing the manipulative military commander who sought to hide behind a politician's mask.
"Lubanga made children train to kill, Lubanga made them kill and Lubanga let the children die ... in hostilities," prosecution lawyer Ekkehard Withopf said in his opening statement.
Lubanga stands charged with abducting children and forcing them to participate in attacks by the armed wing of his Union of Congolese Patriots (UPC) during wars that ravaged the Democratic Republic of Congo.
Thursday's hearing marked the first time prosecution lawyers have presented evidence in a case before judges at the ICC -- set up to try war crimes, crimes against humanity and genocide.
At the start of the hearing, Lubanga, wearing bright blue traditional African dress, introduced himself as the former UPC president.
Provisionally charged with three counts of war crimes, he has denied all accusations against him.
Later on Thursday the defence will give its opening statement and at a press conference Wednesday Lubanga's lawyer Jean Flamme cast his client as a peace-loving politician -- an image hotly disputed by prosecutors.
"Lubanga has told you he was a politician. Lubanga however, is a man with a double face, and the prosecution will show his other face," Withopf said.
The hearing also marked the first opportunity for the victims of Lubanga's alleged crimes to address an international court.
"We hope that the presence of the victims will remind the participants that this hearing is not an intellectual exercise between prosecutor and defence, but that the destruction of thousands of young lives will be at the centre of the discussions," Belgian lawyer Luc Walleyn, representing three Congolese families, told the court.
He stressed that the victims still suffered daily from what has happened to them. "I have nightmares. When I think of some of the things we did I wake up and my ears and my eyes hurt. I hear noises, aircraft and I think other people can hear too and I ask them, but it's just me," Walleyn quoted one of his clients, now barely 15-years-old, telling psychologists. "We represent children whose souls will not rest until justice is done," the lawyer said.
Lubanga, 45, and his militia have been named in connection with a long series of human rights abuses in the north-eastern DRC region of Ituri where inter-ethnic fighting over gold mines and other resources has claimed more than 60,000 lives since 1999, according to humanitarian groups
"The practise of ... using children in warfare represents one of the most brutal and morally troubling crimes against the most vulnerable groups in times of war: children," deputy prosecutor Fatou Bensouda said.
The DRC is among nations with the largest number of child soldiers in the world, the prosecution said. At the height of the war as many as 30,000 children were associated with armed groups.
The confirmation hearing is set to run through November 28, after which the judges must determine whether Lubanga will become the first person to stand trial before the ICC. Their decision is expected late January.
During the 12-day hearing prosecutors will present an overview of the evidence, including written testimony from six former child soldiers. Based in The Hague, the ICC was created by a treaty in 1998 and formally came into being following its ratification in 2002 by more than 60 countries. More than 100 nations have now endorsed the treaty.
Lubanga is the only suspect in ICC custody.

Copyright AFP (Agence France-Presse), 2006