Militia fighting against Colonel Mu'ammar al-Gaddafi have detained about 2,500 people in the capital Tripoli and surrounding areas since taking control of these areas in late August 2011. Most have been held without legal orders and many have been beaten and otherwise ill-treated. The new Libyan authorities – the National Transitional Council (NTC) – have promised to respect international human rights law. In this report Amnesty International urges the NTC to investigate abuses by its supporters as well as by al-Gaddafi forces, and bring the perpetrators to justice.