The commission treats this kind of behaviour very seriously

EC spokesman

The EC said Fridays action was part of a wider investigation into Europe's breweries, which takes in companies in France, the Netherlands, Italy and Portugal.

It said the investigations were still at an early stage.

Carlsberg and Heineken have two months to prepare a written response to the allegations, or risk facing a fine.

"The commission treats this kind of behaviour very seriously, because market sharing is amongst the most blatant forms of anti-competitive practise," it said.

Last year, the commission fined Belgian beer company Interbrew 46.5 million euros ($40m, �28.3m) and Danone, former owner of Alken Maes beer, 44.6 million euros for fixing prices in the Belgian beer market.

Carlsberg said the allegations stemmed from contacts between it and Heineken's former chief executive officers, which it said were simply "courtesy relations and ordinary business discussion".

"There were no discussions of anything we would have benefited from," the company said.