Armed men have forced the closure of five oil facilities in eastern Libya in protest over not being granted more seats in this weekend's first elections since Moamer Kadhafi was overthrown.
"We have shut Al-Sedra, Haruj, Zuwaytina, Brega and Al-Hariga in protest over the distribution of seats in the (incoming) congress," protest leader Ibrahim al-Jadhran told AFP.
Jadhran says he heads the Wadi Ahmar movement which wants seats in the 200-member General National Congress due to be elected on Saturday evenly split along regional lines.
Instead the authorities, citing demographic considerations, have given 100 seats to the western region of Tripolitania, 60 to the eastern region of Cyrenaica, and 40 to Fezzan in the south.
"We will continue our protests until Saturday night. If the authorities do not reallocate seats, we will consider other measures," Jadhran said without elaborating.
An oil industry expert downplayed the disruptions in the east, predicting that it will all blow over after polling, and noting that many major oil firms had evacuated expats anyway, anticipating some unrest.
"This is just people jockeying for position," he said, requesting anonymity.
"In terms of worldwide ramifications, it is a minor disruption because it will be for a short term, until elections are over."
Protest leader Jadhran said that the Wadi Ahmar group has no ties to a Benghazi-based tribal and political faction, known locally as the federalists, which has similar demands and has threatened to boycott the vote.
The move to shut down oil facilities in the east began late on Thursday with armed protesters forcing the closures of Al-Sidra, 35 kilometres (20 miles) west of Ras Lanuf, Haruj, and then heading eastward to Brega.
Earlier on Thursday, suspected arsonists ravaged a depot containing electoral material in the eastern city of Ajdabiya.
And on Sunday, armed men ransacked election offices in the eastern city of Benghazi, cradle of the revolution that ousted Kadhafi last year and a federalist bastion.
-- Attention-seeking behaviour --
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"The situation is the same in Ras Lanuf, Brega, and Haruj," he said.
Groups demanding greater representation in the east are not the only concern to the government and international community ahead of the election.
The weeks before the election have been marred by fighting between different communities, with bloody clashes in western hilltop towns claiming more than 100 lives and fighting in Kufra in the south leaving dozens dead.
Security services have warned that supporters of the former regime may seize the opportunity to disrupt the vote to elect a national assembly, which will be tasked with appointing a new government.
And Islamist groups in the east also oppose the vote, saying the devoutly Muslim country needs no constitution other than the Koran.
The outgoing National Transitional Council said on Thursday that Islamic law (sharia) should be the "main" source of legislation and that this should not be subject to a referendum.
-- Rule change in middle of game --
The new assembly was to have become an interim legislature, appoint a new government and a panel to draft a new constitution.
But on Thursday, the NTC abruptly changed the rules it had itself set, saying the constituent authority must be elected separately rather than appointed, stripping the General National Congress of a core functions.
The amendment came in "response to demands made by a significant part of the population," according to NTC spokesman Saleh Darhoub.
An NTC delegate was more direct, saying its primary purpose was to appease the federalist faction.
Oil production is the major source of government revenues in Libya, and has reached 1.55 million barrels per day, nearing pre-war levels, officials say.
The oil complex at Ras Lanuf lies 360 kilometres (225 miles) west of the eastern city of Benghazi, birthplace of the revolt that ousted Kadhafi, who was captured and killed in October last year.
A former rebel manning a checkpoint on the coastal highway said: "We closed the terminal because we want our demands to be fulfilled. This is an issue of seat allocations."