The United Nations envoy to Libya says uncontrolled militias have caused a surge in unrest there and are illegally holding thousands of people in detention centres, while the weak interim government struggles to assert its authority.
Ian Martin told the Security Council Libya's interim government has taken steps to demobilise former combatants, but is struggling to establish its legitimacy against a proliferation of armed groups.
The BBC reports the Security Council was told on Wednesday recent violence in Tripoli, Bani Walid and Benghazi highlighted the problem.
More than 8000 pro-Gaddafi supporters are being held by militia groups, amid reports of torture. Four died in clashes in Bani Walid, a former Gaddafi stronghold, on Monday.
Mr Martin told the Security Council those clashes between armed residents of Bani Walid and revolutionaries had been misreported as pro-Gaddafi forces retaking the city.
UN human rights chief Navi Pillay says she is extremely concerned about the conditions in which the militias were holding prisoners - mainly those accused of being Gaddafi loyalists and including many sub-Saharan Africans.
