BENGHAZI, Libya — Tribal leaders and militia commanders declared oil-rich eastern Libya a semiautonomous state on Tuesday, a unilateral move that the interim head of state called a “dangerous” conspiracy by Arab nations to tear the country apart six months after the fall of Moammar Gadhafi.

Thousands of representatives of major tribes, militia commanders and politicians made the declaration at a conference in the main eastern city of Benghazi, insisting it was not intended to divide the country. They said they want their region to remain part of a united Libya, but needed to do this to stop decades of discrimination against the east.

The conference declared that the eastern state, known as Barqa, would have its own parliament, police force, courts and capital — Benghazi, the country’s second largest city — to run its own affairs. Foreign policy, the national army and oil resources would be left to the central government in the capital Tripoli in western Libya. Barqa would cover nearly half the country, from the center to the Egyptian border in the east and down to the borders with Chad and Sudan in the south.

Mustafa Abdul-Jalil, head of the Tripoli-based interim central government known as the National Transitional Council, warned the declaration “leads to danger” of eventually breaking up the North African nation of 6 million. But he also said it was to be expected, because the east played a pivotal role in ending Gadhafi’s rule.

The interim leader has not in the past blamed any Arab nation for meddling, while praising Gulf nations like Qatar, which was supportive of the rebels fighting Gadhafi.

Abdul-Jalil appealed to Libyans for patience and resolve in the face of the country’s mounting problems.

Fadl-Allah Haroun, a senior tribal figure and militia commander, said the declaration aims for administrative independence, not separation.

“We are not talking about changing the flag or national anthem. We are talking about different administration, a parliament and managing the financial affairs,” he said.

The east was the cradle of last year’s uprising and civil war that ousted Gadhafi. In the early days of the revolt, the entire east came under opposition control and remained that way until Gadhafi fell in August. The eastern rebels set up the National Transitional Council, originally in Benghazi, which then moved to Tripoli and became the central government.