As always in linguistically divided Belgium's politics, the country's French-Dutch language fault line will play a central role in determining the new coalition government to emerge after the elections.

Since no party fields candidates in both of Belgium's two main regions, winning in Dutch-speaking Flanders, where 60 percent of the population live, is key to national success.

Belgium's 7.7 million registered voters, who are required by law to vote, were casting ballots for candidates vying for 150 seats in parliament and 71 in the senate.

After polling stations close at 1:00pm (1100 GMT) for traditional paper ballots and 3:00 for electronic voting, the first results were expected around 5:00 pm and the final count was due in around midnight.

With most polls putting Verhoftstadt's Flemish Liberal Democrats in fourth place in Flanders, chances are slim that he will return for a third four-year term although he has delivered firm economic growth over the last eight years.

"Whether tax cuts, or reducing unemployment, we need reforms. I hope voters will understand," Verhofstadt told private television channel RTL after casting his ballot.

Leading the pre-vote polls was the Flemish Christian Democrats, making regional Flemish leader and party heavyweight Yves Leterme, 46, the favourite to emerge as prime minister from the round of political horse-trading that will follow the election.

After a short but tense campaign, Leterme appeared calmly confident after he voted, telling RTL: "I slept better last night than the night before... We'll see what responsabilities voters want to give us."

While Leterme's platform of more power for regional bodies goes down well in Flanders, it makes French-speakers uneasy in Belgium's poorer French-speaking southern half, Wallonia.

Although he is perfectly bilingual thanks to his francophone father and Flemish mother, Leterme has so far made little effort to bridge the linguistic divide that cuts through Belgian politics and life.

In addition to disparaging Wallons for their failure to learn Dutch, he has stoked controversy in the past in Wallonia by saying that Belgium was an "accident of history" and that the country has no "intrinsic value"

Tensions over Belgium's French-Dutch divide are running particularly high after the French-language state television channel aired a spoof 'breaking news' story in December saying Flanders had voted to break away.