Vlaams Belang supporters celebrated their best ever result

The anti-immigrant Vlaams Belang (Flemish Interest) party won about 20% of the vote in Dutch-speaking Flanders.

However it was knocked from first to second place in its traditional heartland - the city of Antwerp.

In the past other parties have formed coalitions to keep Vlaams Belang out of power, even where it has come first.

They are expected to try to do the same again.

Protest vote

Vlaams Belang campaigns on a platform of independence for Flanders, the richer Dutch-speaking part of Belgium, and an anti-immigration integrationist stance towards minorities.

But it is perhaps primarily a place for the protest vote, for people to register their dissatisfaction with the long-standing political status quo, says the BBC's Jonny Dymond in Brussels.

Guy Verhofstadt acknowledged the scale of his party's defeat

The status quo seems to be unpopular at the moment, he adds, with the far right making what it calls "spectacular" gains.

The lead party of the national coalition - the Liberal Democrats - has seen its share of the vote slip away.

"This is a landslide victory," said Vlaams Belang party chairman Frank Vanhecke.

However, there was some consolation for the mainstream parties in Antwerp, the home of Vlaams Belang, where it suffered its only significant setback.

Even though it increased its share of the city's vote to 33.5%, it was overtaken by the Socialists, inspired by their popular mayor Patrick Janssens, who made dramatic gains to 35.3%.

"It shows that it is possible to stop Vlaams Belang with a positive project," Mr Janssens said.

Socialists suffer

Belgian Prime Minister Guy Verhofstadt acknowledged the scale of his party's defeat, with less than a year to go before parliamentary elections.

"The average trend of the Flemish Liberal Democrats is not so good," he said.

"We must acknowledge that the government has had a few bad months and we know that whoever leads faces the most fire."

Meanwhile, in Wallonia, the French-speaking part of Belgium, Mr Verhofstadt's coalition partners, the Socialists, lost ground badly.

The party, embroiled in a corruption scandal, was forced to give up seats in the cities of Charleroi, Namur, and Liege.