FILE PHOTO: A former child soldier holds a gun as they participate in a child soldiers' release ceremony, outside Yambio Thomson Reuters By Tom Miles

GENEVA (Reuters) - Thousands of child soldiers dragged into South Sudan's civil war are unlikely to be freed soon because aid agencies lack the funds to look after them, a U.N. envoy said on Tuesday.

The government signed a peace deal with rebel factions in September to end a civil war that killed at least 50,000 people, but many children who were forced into the conflict are still stuck in military camps in the bush, Virginia Gamba, U.N. envoy for children and armed conflict, said.

Gamba, who has spoken to former child soldiers in the country, said a lack of resources to re-integrate the children meant they remained at extremely high risk of abuse.

Since January, 900 child soldiers have been freed and Gamba expects a further 1,000 releases by the end of the year. But there are many more, she told reporters.

"The first group of released children ... kept telling me that at least two or three of their friends were still in the bush waiting to be released or waiting to be negotiated and asking me to intervene on their behalf," she said.

"We are talking of thousands still out there."

U.N. funds for reintegrating children had halved over the past seven years while needs doubled, and aid workers could not cope with a sudden mass release, she said.

"For every day that a kid is in the bush they will be revictimised, there’s just no question about it."

After being abducted, children might be raped or sent to attack their own families to sever their ties to home. Escape attempts were punished by hand amputation or molten plastic poured onto the skin, Gamba said: "They were terrified."

Four-fifths of the violations were committed by the army, but all warring parties were guilty, Gamba said.

A South Sudan army spokesman declined to comment.

Gamba said the number of violations of children's rights was greater than in Syria and Afghanistan.

"It is really huge, it’s quite gross. I mean, decapitation of children, the use of sexual violation against very small children as part of a weapon and a tactic of war to cow communities, the abduction of children, the recruitment of children, forced use of children in support of war efforts."

South Sudan has agreed a joint action plan with the United Nations that would allow aid workers to reach deep into the former war zone and verify child numbers in military camps.

Freed children - 40 percent of them girls - might get six months of help to learn a skill like carpentry or sewing so they could fend for themselves, but they would never go to school.

"These kids are condemned for the rest of their life ... their dreams will never be achieved," Gamba said.

(Reporting by Tom Miles, additional reporting by Denis Dumo; Editing by Robin Pomeroy)