The report, drafted by the UN rights office and the UN mission in Libya (UNSMIL) revealed a plethora of violent attacks against activists across the conflict-ravaged country, and even in some cases after they have fled abroad.
It pointed to the recent case of prominent civil society activist Intessar al-Hassaeri, whose body was discovered last month along with that of her aunt stuffed in the boot of a car in Tripoli.
A number of murders in Benghazi last year also remain unsolved, including that to newspaper editor Muftah Abu Zeid, rights defender Salwa Bughaigis and two young civil society activists, Tawfik Bensaud and Sami al-Kawafi.
"Many have been killed," Claudio Cordone, head of UNSMIL's human rights division, told reporters in Geneva.
He said that it was impossible to have a clear overview of the numbers, but that the situation for human rights defenders had obviously deteriorated significantly since the escalation in fighting last May.
Cordone pointed out that the prosecutor who had been looking into Bughaigis' murder had disappeared.
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The country, he said, had reached "its most repressive since the revolution."
"Basically everybody is exposed."
Libya has been in turmoil since the 2011 overthrow of longtime leader Moamer Kadhafi in a NATO-backed uprising.
It has had two parliaments and governments since Tripoli was seized in August 2014 by the Fajr Libya militia coalition and the internationally recognised government fled to the country's far east.
In the current situation where an estimated 200,000 to 300,000 people are armed – 10 times the 20,000 to 30,000 who fought during the revolution – any criticism against different sides is being met with reprisals, Cordone said.
Libyan activists sometimes even continue to face threats and attacks even after they have fled the country, according to Wednesday's report.
In one case, Manal al-Bousefi, a journalist and women's rights defender in Benghazi who left the country last August, said she was stopped by a car with Libyan license plates in an unnamed country.
"The passenger threw a cup of coffee at her warning: 'You... activist and journalist... Next time it will be acid'," the report said.