Enforced disappearance describes the secret detention or abduction by a state or third party. The U.N.-backed Commission of Inquiry on Syria found a nationwide pattern of the practice during Syria's civil war.
The report said it found the Syrian government targeted family members of activists, defectors or rebel fighters as a punitive measure. The practice was conducted by anti-government forces as well.
"In all the cases documented by the commission, survivors of enforced disappearances described being subjected to torture during their detention," the United Nations report said. "The commissioners note that this underscores a deeply disturbing trend which sheds more light on the systematic use of torture."
U.N. investigators found authorities often refused to provide information about the fate of those abducted or detained. The commission said those family members seeking information about relatives who may have been subjected to the practice were often arrested.
The commission based its reporting on first-hand interviews conducted between March 2011, the start of the Syrian conflict, through November.
U.N. High Commissioner for Human Rights Navi Pillay has said the government of Syrian President Bashar Assad may be responsible for war crimes and crimes against humanity.