"Young girls are being taken hostage and abducted for marriage to military commanders and long-haul truck drivers," said the Economic Commission for Africa, a UN body based in Ethiopia.
The study singled out Uganda, Sudan and Sierra Leone as three countries where abductions continued to increase.
According to the UN Children's Fund more than 10 000 children have been abducted since June 2002 in northern Uganda by the Lord's Resistance Army (LRA), an armed rebel group fighting the government in Kampala.
The Hague-based International Criminal Court said the figure might be as high as 20 000.
"As part of initiation into the LRA rebel movement, abducted children are forced into committing inhuman acts, including ritual killing and mutilations," the ICC said. "A key issue will be locating and arresting the LRA leadership."
The world court said this would require the active co-operation of member states and international institutions to back the efforts of Ugandan authorities.
ECA said many women and children are being held hostage for as long as 10 to 15 years.
"The Ugandan government has implicitly renounced its primary jurisdiction against major offenders," said David Donat Cattin, legal advisor for the international law and human rights programme at Parliamentarians for Global Action.
"Other states facing similar situations should follow Uganda's precedent in welcoming the initiation of ICC proceedings. It is now the duty of the (ICC) prosecutor to investigate in all directions and search for the truth on the atrocities perpetrated in northern Uganda," Cattin added.
Casey Kelso, international co-ordinator for the London-based Coalition to Stop the Use of Child Soldiers, told IPS there was strong evidence that abductions of children in northern Uganda by the LRA were at "the highest point of the conflict's 17-year history".
"We are particularly concerned about the plight of girl children in conflict zones, and the reports from northern Uganda confirm that the girl child is under attack from gender-based violence and abductions."
Jo Becker of Human Rights Watch said the abduction of children for use as soldiers, sex slaves and labourers was "one of the most abhorrent aspects of armed conflicts".
"Clearly, one of the worst cases in the world today is northern Uganda, where abduction has reached catastrophic levels," she said.
"We know that as many as 20 000 children have become 'night commuters' - walking long distances to urban areas each night to sleep in churches, bus stations and in open spaces -- hoping to escape abduction," Becker said. - Sapa-IPS