Riga/Vilnius - Lithuanians are voting Sunday in an unusual double poll that includes a general election and a referendum on the future of the country's Soviet-era Ignalina Nuclear Power Plant.

Voting stations across the Baltic nation opened at 7 am (0400 GMT) local time and will close at 8 pm for some 2.7 million voters to decide the future composition of the parliament, the Seimas.

At total of 141 members of parliament will be returned using a combination of proportional representation and majority voting. The Seimas is elected for a four year term.

A further 71 MPs are elected by means of proportional representation from national party lists with the remainder fighting it out to win outright majorities in local constituencies.

The difficulty of winning more than 50 per cent of the vote in an election with 17 political parties means a second round is usually called for, scheduled to take place in two weeks' time.

Parties need to win at least five per cent of the vote to be entitled to MPs via the proportional representation route.

A total of 1,603 candidates are standing, with 764 hedging their bets by running in both multi-mandate and single-mandate districts.

As well as having the opportunity to vote for their preferred candidates, voters will be presented with a separate ballot paper for the referendum, asking them "Do you approve of the continued use of the Ignalina plant until a new one can be built?"

Lithuania agreed to close the Ignalina plant by 2009 as part of its deal to join the European Union in 2004. A planned replacement, to be built jointly with Estonia, Latvia and Poland, is unlikely to be ready before 2015.

Politicians and the public fear that a six-year energy gap would increase Lithuania's energy dependency on Russia and could ruin the national economy.

A large majority is expected to back an extension of the nuclear plant's lifespan, which would then be used as evidence in efforts to win a reprieve from EU lawmakers.

Technically, the results of the referendum are non-binding and it is only considered that the people have spoken if at least half of eligible voters participate.

First official results are expected to be announced in the early hours of Monday morning. (dpa)