Migrants and refugees are subjected to "unimaginable horrors" from the moment they enter Libya, a report from the UN human rights office says. The report says they are tortured, raped and killed in detention.

It contains 1300 firsthand accounts gathered by UN human rights officers in Libya as well as countries of origin such as Nigeria, and destination countries like Italy.

In each of the 11 detention centres visited by UN human rights officers, an overwhelming majority of women and teenage girls said they had been gang-raped by people smugglers.

The climate of lawlessness in Libya is fertile ground for illegal trafficking, the UN says, but the report also criticises Europe's policy of preventing migrants crossing the Mediterranean. It says that the push back simply returns migrants to the same horrific conditions in Libya, leaving thousands of desperate people trapped there.