Thomas Lubanga, a former Congolese rebel leader, will remain in jail in The Hague after the appeals panel of the International Criminal Court (ICC) said it feared he might not reappear if another trial is ordered.
Judges at the ICC ordered Lubanga's trial halted on July 8, saying that Luis Moreno-Ocampo, the court's chief prosecutor, had not complied with an order to turn over certain information to his defence.
The court later ordered his release on the grounds he could not be held in custody if it were unclear when or if his trial would ever resume. The prosecutors had appealled against that decision.
"Today, the appeals chamber of the ICC granted the suspensive effect to the prosecution's appeal" against a July 15 decision to free Lubanga following the suspension of his trial, the court said in a statement on Friday.
"Therefore the accused will remain under custody of the ICC pending the final decision on the appeal."
Lubanga is accused of enlisting and conscripting children aged under 15 for his Union of Congolese Patroits, to kill members of a rival tribe in the 1998-2003 war in the Democratic Republic of Congo.
He has pleaded not guilty and described himself as a politician, not a warlord.
Lubanga had insisted he could not flee if released as he has no travel documents and pledged to remain "at the disposal of the court" throughout the appeal.
Lubanga's trial, the ICC's first, was initially to have started in June 2008 but was stalled until the following year when the court ruled that prosecutors had wrongly withheld evidence potentially favourable to his defence.