Armed opposition groups stormed election headquarters in the eastern city of Benghazi during the weekend calling for greater autonomy for the region.
Deputy head of the High National Election Commission, Emad al-Sayeh, said from Tripoli that security forces in Benghazi were outnumbered, the Tripoli Post reports.
Protesters, according to the news agency, carried signs calling interim leader Mustafa Abdel Jalil "a traitor of Cyrenaica."
In February, tribal and political leaders in Benghazi declared they would form an autonomous government while leaving foreign policy, energy and military matters in the hands of the central government in Tripoli.
Jalil described the move as a conspiracy hatched by remnants of the regime of former Libyan leader Moammar Gadhafi.
Benghazi was the sight of the first demonstrations against Gadhafi's government in February 2011. The city was part of Cyrenaica, which, along with Tripolitania and Fezzan, formed the three semi-autonomous states of Libya in the 1950s.
Libyans next weekend head to the polls to choose their new parliamentary leaders. Some groups in eastern Libya have called for a boycott of the vote, the first such contest in Libya in a generation.