Traffic moves during a sand storm in the Libyan capital Tripoli on Thursday. The United Nations expressed deep concern that day over rising violence in Libya’s capital, warning the clashes risk mass displacement and put civilians in grave danger. Libya has remained deeply divided since the 2011 NATO-backed revolt that toppled and killed longtime leader Moamer Kadhafi. Clashes flared again Wednesday in key areas including Tripoli’s port, in what a security source called ‘urban warfare.’