Libyans vote for a national assembly on Saturday, the first election since Muammar Gaddafi's ouster, after a string of acts of sabotage that have stoked tensions in the east of the country.

Polling stations are scheduled to open at 8 am (5 am GMT) and will close 12 hours later.

The vote will likely be a very different experience for residents of Tripoli, which has enjoyed a spell of calm than in those of cities in eastern Libya which have been subject to outbreaks of deadly violence and threats to disrupt the vote.

On Friday, gunfire struck a helicopter in eastern Libya killing an election worker.

Ian Martin, head of the United Nations mission to Libya, urged 'all voters to exercise their hard-earned democratic right to elect their National Congress representatives' while condemning the deadly attack.

The Brussels-based International Crisis Group has warned that the electoral process in Libya is 'imperilled by armed protesters who... are threatening to disrupt the vote in the eastern part of the country'.

Also in the run-up to the polls, five oil facilities have been forced cease production by armed protesters who want greater representation for the east in the incoming 200-member congress.

Armed protesters last Sunday ransacked the office of the electoral commission in Benghazi. Arsonists in nearby Ajdabiya later set fire to a depot with polling material.

The make-up of the congress has been a matter of heated debate, with political factions such as the federalist movement calling for more seats.

The ruling National Transitional Council (NTC) says seats were distributed according to demographic considerations, with 100 seats going to the west, 60 to the east and 40 to the south.

But factions in the east want an equal split of the assembly's seats and have threatened to sabotage Saturday's vote if this demand is not met.

The authorities dismiss such groups as a disruptive minority, pointing out that more than 2.7 million people, or around 80 percent of the eligible electorate, have registered to take part in the historic poll.

Libya has not seen elections since the era of late monarch King Idris whom Gaddafi deposed in a bloodless coup in 1969.

Parties were banned as an act of treason during Gaddafi's 42 years of iron-fisted rule. Now there are 142 parties fielding candidates.

A total of 80 seats are reserved for party candidates while 120 seats are open to individual candidates. Altogether, 3,707 candidates are running in 72 districts across the country.

From the parties, the coalition of ex-war time prime minister Mahmud Jibril is seen as a key contender among liberals, facing stiff competition from two Islamist parties -- Justice and Development and Al-Wattan.

The incoming congress will have legislative powers and appoint an interim government. But it no longer has the right to appoint a constituent authority, under a last-minute amendment issued by the outgoing NTC.

The winds of the Arab Spring that ushered Islamists into power in neighbouring Tunisia and Egypt may well bring the same result on Saturday in the first national election since Gaddafi was toppled.

A February 2011 uprising ended more than four decades of the dictator who was killed while on the run last October.