UNITED NATIONS — United Nations investigators say in a new report that children in Syria have been sexually abused in government detention, recruited to fight with the opposition, tortured and used as civilian shields.

The report, the first to assess the impact of the nearly three-year-old Syria war on children, was quietly presented to the Security Council last week, as Syrian government and opposition representatives met in Switzerland for peace talks under the auspices of the United Nations.

Secretary General Ban Ki-moon’s special representative for children and armed conflict, Leila Zerrougui, is scheduled to brief the Council next week on the report, which was not released publicly until Monday.

It estimated that at least 10,000 children had been killed and that “grave violations against children” had been committed by “all parties to the conflict” since it began in March 2011. While the report did not discuss accountability, the evidence it presents will inevitably invite discussion about how to pursue accountability for accused war criminals.