GENEVA (AP) — The U.N.'s human rights office says interviews of migrants in Libya have revealed that the "overwhelming majority" of women and older girls reported being gang-raped by smugglers or traffickers.

The Office of the U.N. High Commissioner for Human Rights said it turned up "unimaginable horrors" among migrants who seek to reach Europe through largely lawless Libya.

The office and the U.N. support mission in Libya issued a report Thursday covering a 20-month period through August.

A statement said investigators pulled together 1,300 first-hand accounts for the report that details "a terrible litany of violations and abuses committed by a range of State officials, armed groups, smugglers and traffickers against migrants and refugees."

Those included unlawful killings, torture, arbitrary detention, gang rape, slavery, forced labor and extortion.