"There are problems at the ministry of interior and disputes between the security services," Fawzi Wanis al-Kadhafi, head of the supreme security committee in Benghazi, told AFP.

"Working conditions are not the same as before, so I decided to resign," he added.

The supreme security committee, which falls under the interior ministry, was established by ex-rebels after the overthrow of Muammar Gaddafi last year in a bid to restore order.

Libya's interior minister on Monday announced the sacking of deputy interior minister for the eastern region, Wanis al-Sharef, and the head of national security for Benghazi, Hussein Bou Hmid.

The resignation comes a week after Ambassador Chris Stevens and three other Americans were killed as the Benghazi consulate came under fire from rocket-propelled grenades.

The attack was orginally blamed on protesters angered by an anti-Islam film made in America but neither US or Libyan officials have excluded the possibility that it was a pre-planned attacked supported by Al-Qaeda.