A revolt by German dairy farmers gained traction Thursday, with the price for milk rising as farmers all over the country poured milk down drains in a boycott of dairy factories.

Romuald Schaber, president of the BDM association of German dairy farmers, which launched the strike on Tuesday, said Italian farmers had promised to cut off their supplies to German dairy companies from Friday to step up the campaign for higher farm-gate prices.

He said a similar declaration of solidarity Thursday had come from counterparts in Belgium after the BDM appealed to farmers outside Germany not to fill the shortfall. The German farmers are demanding a farm-gate price of 40 euro cents (62 dollar cents) a litre for milk.

Uwe Kockerbeck, chief executive of an independent milk trader, Apollo Milchprodukte, said the strikers' target price had been reached already on the spot market since the boycott began. The spot price had risen from 28 cents to more than 40 cents.

'We can't import enough milk to cover the shortfall,' he said at his company's office in Kleve near the Dutch border.

Schaber's group, which hopes a successful boycott will make that price rise permanent, claimed the boycott had reduced the supply of milk to German pasteurizing plants and cheese factories by 70 per cent.

He estimated that 70,000 of Germany's 100,000 dairy farms had joined the boycott.

However Germany's national farmers' union dismissed the claim. A spokeswoman there said only 10 to 20 per cent of farmers had joined the BDM's campaign, with most continuing to supply milk. She said she knew of no substantial support abroad for the BDM.

The farmers blamed powerful dairy companies for depressing the farm-gate price of milk, and are also angry at EU plans to increase output quotas. Brussels says it must respond to growing global demand for milk, especially from booming Asian nations.

Before the boycott, the dairy factories of Germany were paying 27 cents a litre in north Germany and 35 cents a litre in south Germany for milk, according to BDM data.