Belgium is historically one of the world's top beer countries but Thomas Costenoble, organiser of the Brussels Beer Challenge, fears that trouble is brewing.

This international contest in the Belgian capital, now in its fifth year, features 1,250 beers from 36 countries and 80 judges to sample the tipples on offer.

But Belgians increasingly fear that their centuries-old dominance is at risk from foreign upstart beers that are not afraid to break with tradition.

"Belgium is still a reference point," Costenoble tells AFP, but adds that in certain categories Belgian beers are "no longer as assured in terms of quality."

In 2015 the first prize went to an IPA, or Indian Pale Ale, from Seattle in the United States -- the first time Belgium had surrendered the top spot.

Belgium is still the top competitor at the Brussels challenge with 240 beers but it is closely followed on 210 by both the United States and, perhaps surprisingly for a country best known for its wines, Italy.

Globally the beer market is evolving to focus on artisan brews, leading to smaller "microbreweries" that focus on quality rather than quantity.

In Belgium the number has grown from 127 to 199 between 2009 and 2015 and the trend has been the same internationally.

The United States has seen the number of breweries explode from 1,596 to 4,225 over the same period, while in the Netherlands the number has more than tripled from 117 to 401 and in Italy from 256 to 914, and numbers have doubled in France (332 to 663) and Britain (745 to 1,424).

- 'Belgium always unique' -

"The UK and the US are without a shadow of a doubt leading the way in terms of innovation in beer. But it's actually very high quality innovation," said Melissa Cole, a British author and beer specialist who has been on the jury of the Brussels Beer Challenge since the start.

"France and Italy are still not as high up there in terms of their quality of beer across the board. There are a lot of beers that are still not being made properly, not being packaged correctly."

Belgium's huge range of beers -- from sour lambics to fruity krieks, and from dark abbey beers to lagers -- meant it remained ahead of the pack but needed to keep innovating, added Cole.

"Belgium will always be unique. It has total geographical protection for its lambics. That's a very vital and fantastic part of its tradition," she said.

"Belgium up until five maybe seven years ago had exactly the opposite problem (as its competitors): pretty technically excellent in most places but actually really a little backwards in innovation. And I'm pleased to see that that's changing."

Older family breweries like Cantillon or Lindemans are now becoming more dynamic in the face of newer Belgian arrivals like Brasserie de la Senne, she said.

The Belgians are also adopting, like many others, the IPA, the beer of the moment with its fresh and less sugary taste.

"A very hoppy beer -- a nightmare for older consumers and for the industry," says Italian professional taster Lorenzo Dabove, with a smile.

His country is one of the most dynamic in this market having launched itself into the "artisan beer" revolution since the mid-1990s, with some small Italian breweries now exporting up to 70 percent of their production.

But the true test of whether Belgium's rivals are catching up will be in the tasting: the results of the Brussels Beer Challenge will be unveiled on November 21.