The United Nations has added three Malian militias and Syria's main rebel force for the first time to an annual "list of shame" of armed groups that recruit children.

The list was part of report released Wednesday that also harshly criticized the Syrian regime over accounts that it has detained and tortured minors to extract information on rebel groups.

The annual report on children of armed conflict covered 21 countries, detailing new abuses against children in some conflict zones and progress in others. Fifty-five armed groups from 14 countries were included in "lists of shame," some for recruiting children and others for other abuses against minors. The Syrian government forces were added to a list of groups that sexually abuse children.

Hundreds of children, mainly boys between 12 and 15, were enlisted to fight by armed groups who fought over Mali's north last year, according to the report by UN Secretary-General Ban Ki-moon.

The "list of shame" of children recruiters included the Tuareg group MNLA and two Islamic groups, MUJAO and Ansar Dine.

The UN also received accounts of pro-government militias in Mali recruiting children.

The UN report also accused the Syrian armed forces and intelligence services of torturing minors, mostly boys, with electric shock, beatings and sexual assault. Some minors, related to opposition fighters, were held for ransom to force parents or other relatives to surrender, the report said. One 16-year-old boy from Idlib reported witnessing a 14-year-old friend sexually assaulted and killed while in government detention, the report said.

"The toll on children of the conflict in the Syrian Arab Republic is unacceptable and unbearable," Ban said in the report. He called on Assad's government "to put an end to the detention and any form of ill-treatment, including torture, of children for alleged association with the opposition."

Ban said there were a growing number of reports of the Free Syrian Army, the main rebel umbrella group, recruiting children, mostly between 15 and 17.

The Syrian and Malian missions to the U.N. did not immediately return requests for comment.

The report detailed progress in protecting children in other conflict zones. New action plans were signed in South Sudan, Myanmar, the Democratic Republic of Congo and Somalia to prevent the recruitment of child soldiers, the secretary-general reported.

"In 2012, boys and girls from several countries had better protection from the effects of conflict, but new and ongoing crises in Mali, Central African Republic and Syria for example had -- and continue to have -- a devastating effect on children," said Leila Zerrougui, the Special Representative of the Secretary-General for Children and Armed Conflict.