Hundreds of tractors were descending on Paris in a boisterous protest by farmers blocking highways to express their anger over falling French food prices and high taxes.

They are protesting about increasingly slim margins they blame on cheap imports and high payroll charges, which they say make them unable to compete against Germany, much less Eastern Europe or beyond, and they are seeking support from the French government and the EU.

Tractors bearing spray-painted slogans such as "Our charges are killing us," moved slowly along major arteries to the capital, squeezing past tollbooths. They planned to gather at the Place de la Nation in eastern Paris, and some farmers want to head to Parliament.

Protest organiser FNSEA, France's largest farming union, said 1,500 tractors from around the country were planning to take part.

"It's not popular to annoy all the people on their way to work," said farmer Pierre Bot, from Vauhallan, south of Paris. "Nevertheless, it's one of the only ways to make ourselves heard.

Like many small farmers, he feels increasingly squeezed out by factory farms and fears for the future. Farming "is part of the French identity," he said.

It is also part of a larger debate over European farming and how to keep it globally competitive. A pan-European protest is expected on Monday in Brussels during a meeting of EU agriculture ministers.

French farmers have been particularly vocal this summer, blocking roads on the border with Germany and major tourist destinations such as Mont-Saint-Michel peninsula on the Atlantic.