Tribal chiefs and militia commanders in Libya's east have declared semi-autonomy for the oil-rich region. They made the announcement at a meeting in Benghazi.
Civic leaders from the area known as Barqa, or Cyrenacia, said they had been neglected for decades under Muammar Gaddafi.
The new region stretches from the former dictator's birthplace of Sirte to the Egyptian border. It also holds the bulk of Libya's oil reserves.
The Benghazi gathering also named a leader of the breakaway region. It decided on Ahmed al-Zubair, a cousin of King Idriss. Zubair is also a member of the National Transitional Council, which opposes a federal Libya.
Ministers in Tripoli fear it could lead to the nation's break-up.
State television on Monday broadcast footage of a protest against the breakaway.
Libya had a federal system of government until it was abolished by Idriss in 1963