The UN seretary-general's special acting representative to Libya called on Thursday for an "investigative mechanism" to be established for human rights abuses.
Stephanie Williams told the UN's Human Rights Council that the body should establish the mechanism "given the ongoing serious violations occurring every day in the country."
A Human Rights Council mandate to establish an investigative mechanism would be both the simplest and strongest basis for promoting much needed accountability in Libya," she added.
Williams catalogued a litany of abuses in the country which descended into conflict after the toppling of dictator Muammar Qaddafi in 2011.
Mass graves have been discovered in Tarhuna, a town recently captured by forces loyal to the Government of National Accord (GNA)Â from the rival Libyan National Army.
The GNA has asked the UN to help investigate the sites.
"Serious violations of human rights and humanitarian law have continued to be committed with complete and total impunity in Libya," Williams added.