The UN mission in the Central African Republic (CAR) released rebel fighters accused of shooting a UN peacekeeper, confidential documents seen by the BBC show.
The two men were handed back to their commander in 2015 despite injuring the UN peacekeeper - a war crime under international law.
Because the incident happened shortly before crucial elections, UN officials chose to "appease the electoral process" by "set[ing] the alleged war criminals free, handing them over", a UN report says.
This revelation is the latest blow for a peacekeeping mission beset by problems.
The incident itself took place in December 2015.
