Tribal and political leaders have declared Libya's oil-rich eastern region of Cyrenaica as autonomous.
The move raises concern that the country may break up in the wake of Muammar Gaddafi's downfall.
At a conference attended by about 3,000 people in Benghazi, the major eastern city where the eight-month uprising against Gaddafi began, they also called for a return to federalism in Libya.
"A federal system is the choice of the region" of Cyrenaica, which stretches from the central coastal city of Sirte to the Egyptian border in the east, the leaders said in a joint statement.
"The interim council of Cyrenaica was established under the leadership of Sheikh Ahmed Zubair al-Senussi to manage the region's affairs and defend the rights of its population," read the statement, which was posted online.
Ahmed Zubair al-Senussi, a member of Libya's ruling National Transitional Council (NTC), was elected leader of the region.
The newly-created body will work within the framework of Libya's interim government, which it considers to be "the symbol of the country's unity, and its legitimate representative in international forums".
The proponents of autonomy say the move derives its legitimacy from the 1951 constitution, which was adopted under the monarchy of King Idris and which divided Libya into three states - Cyrenaica, Tripolitania and Fezzan.
