French cattle farmers launched protests against Carrefour on Tuesday to demand higher beef prices from Europe's biggest retailer, in the latest sign of tension in the livestock sector after a price row involving dairy giant Lactalis.

Beef producers in France have been struggling for years in the face of declining consumption. Prices have been dented further this year by a downturn in the dairy market, which has led farmers to send more dairy cows for slaughter.

After dairy farmers last month staged protests against Lactalis, eventually securing higher milk prices for this year, farmer unions are targeting Carrefour supermarkets this week to seek a price rise aimed at covering production costs.

A first protest took place on Tuesday morning at a Carrefour store near the northern town of Rouen and will be followed by wide-scale action on Wednesday including in Paris, according to beef farmers group FNB, part of France's main farm union FNSEA.

Farmer groups say Carrefour has opposed an initiative being piloted by rival supermarket chain Systeme U that commits to paying higher prices to farmers for beef that meets certain quality specifications. They say that without Carrefour's backing there is little chance of a broad improvement in prices.

"We condemn the policy of ever lower prices pursued by Carrefour," Sylvain Gangneux, a local FNSEA official in Normandy who participated in Tuesday's protest in Rouen, told Reuters.

"We are asking for prices that cover our production costs."

Carrefour had no immediate comment.

Farmers in Rouen stopped shoppers outside the store to explain their case, but say they could go further on Wednesday and block access, Gangneux said.

The FNB says months of talks with Carrefour have failed to broker an agreement and that the retailer's prices are about 1 euro below the 4.50 euros a kilo average that would meet their costs.

France, which has the European Union's largest agricultural sector and is the bloc's biggest cattle producer, is also feeling the pain of a Russian embargo on Western food products, as well as an outbreak of cattle disease bluetongue last year that cut off some export markets.