Manila, June 30 -- The UN Human Rights Office said Tuesday it is "horrified" by the recent discovery of mass graves in and around the Libyan city of Tarhuna.

UN Human Rights Office spokeswoman Liz Throssell said her office was "horrified by the discovery of mass graves in Tarhuna and its surroundings".

She was answering written questions from the Anadolu Agency.

"We had already called on June 18 for a prompt, thorough, effective, transparent, and independent investigation to establish the facts and circumstances of human rights violations and abuses perpetrated by all parties in Libya," she said.

She said her office did not contact Libyan authorities regarding the mass graves, but that UN Libyan Support Mission (UNSMIL) had closely foll...