Farmers dumped mounds of potatoes in central Paris and manure at government buildings in other towns as they urged their countrymen to "Eat French" in a day of national protests.

Fed up with environmental regulations and a downturn in agricultural markets, farmers piled 50 tonnes of fruit and vegetables at the Place de la Republique in Paris, then bagged it for passers-by.

Farmers fear that falling prices linked to Russia's import embargo and big harvests in the European Union this summer will cut farm incomes in the bloc's largest agricultural producer after an average drop of 20 percent in 2013.

"Clearly we are expressing our annoyance, and the annoyance of the entire farming world," Damien Greffin, head of the FNSEA union in Paris region, told Reuters.

"Today, a farmer devotes most of his time to administration and paperwork rather than production to feed the population, and this is completely unacceptable."

Wednesday's day of action called by the FNSEA brought around 36,000 farmers out onto the streets across France, accompanied by hundreds of tractors, the union said.

Farmer frustration over red tape and a deteriorating economic outlook has led to more than 150 protests around the country since late August, the FNSEA said.

In an extreme case, vegetable growers in Brittany set fire to public buildings in September.

The government has condemned such violent incidents but has also tried to address farmer grievances at a time when unpopular Socialist President Francois Hollande is facing discontent due to a struggling economy.

"EAT FRENCH"

Anger has notably built up following controversy over a dam project in the southwest designed to allow irrigation for farms and over environmental rules after the government extended a list of water protection zones to limit nitrate pollution.

An environmental protester died last month during clashes with police at the site of the planned reservoir, where work has since been suspended by the local authorities.

In several towns, farmers used tractors to dump livestock manure outside local government buildings, displaying slogans like "Too much biodiversity is harmful".

The FNSEA is also calling for French farm produce to be given a bigger place in the country's canteens and restaurants, supported by an "Eat French" slogan.

As part of Wednesday's action, farmers carrying out checks on lorries delivering food to the French finance ministry said they had found Moroccan tomatoes and Italian apples.

In Paris, passers-by expressed support for French produce.

"If everyone made the effort and paid a little bit more, they could eat quality food and get the French economy moving again, and I think we really need that," said Christine Fouquet.

Agriculture Minister Stephane Le Foll, regularly criticized by farmer groups for advocating environment-friendly practices, said after a weekly cabinet meeting that farmers' discontent was "justified".

To offer short-term relief for farmers, the government announced last month the early payment of some annual EU subsidies.

It is also trying to find alternative export markets to Russia. Le Foll requested last week during a visit to Tunisia that the north African state authorize the import of French apples.