Ugandan military officials this week announced the capture of LRA commander Ceasar Achellam. Radhika Coomaraswamy, U.N. special envoy for children and armed conflict, said Achellam was responsible for abuses against children.
The LRA is suspected of using child soldiers in its militant campaign. Girls are used as sex slaves, the United Nations said, and the LRA has a reputation for killing and mutilating its victims.
"The arrest and subsequent prosecution of Achellam would send a strong message to the LRA leadership that they will be held accountable for their actions," Coomaraswamy said in a statement.
Uganda, however, has adopted a general amnesty for LRA members despite accusations of mass abuses. The special envoy called on authorities there to bring Achellam to justice.
LRA leader Joseph Kony remains at large despite a 2005 indictment by the International Criminal Court on more than 30 counts of violations of international law, including war crimes.
U.N. officials had warned that renewed pressure on the LRA could prompt the militant organization to go on the offensive.