text:  BBC News. The United Nations Human Rights Office has said it's following up reports of a mass grave in the desert along the Libya-Tunisia border. The High Commissioner, Falka Tuuk, said his team had been informed of some disturbing developments in Libya. He denounced widespread violations against migrants and refugees and urged the two countries to investigate the alleged crimes in line with their responsibilities. Mr Tuuk added that the relatives of the victims had every right to know the truth.