Farmers' leaders in the Paris region on Saturday promised to mount a "siege" on the French capital next week to pressure the government into meeting their demands on pay, tax and regulations.
On Monday afternoon farmers from all the regions around Paris belonging to the FNSEA farmers' union or the Jeunes Agriculteurs ("Young Farmers"), "will begin an indefinite siege of the capital," they announced.
The two unions represent most farmers throughout the country.
"All the major roads leading to the capital will be occupied by farmers", they added.
Farmers from the Lot-et-Garonne, one of the hotspots of the protest movement in southern France, had already announced their intention to "go to Paris" on Monday.
They intend blockade the massive Rungis wholesale food market south of the capital.
French farmers are furious at what they say is a squeeze on purchase prices for produce by supermarket and industrial buyers, as well as complex environmental regulations.
But the last straw for many was the phasing out of a tax break on diesel for farm equipment.
Saturday's announcement came the day after French Prime Minister Gabriel Attal announced a number of concessions after farmers blockaded major routes into Paris and in the south of the country.
"You wanted to send a message, and I've received it loud and clear," said Attal, who is facing his first major crisis as prime minister.
Attal said the government would "put an end" to the rising cost of diesel fuel used for farming machinery, a consequence of tax breaks on the fuel having been phased out.
There would also be an emergency fund to help cattle farmers battle illnesses among their livestock.
Early on Saturday, some road blocks were being lifted and traffic began running normally on motorways.
But the latest union announcement puts the pressure back on Attal.
Attal's announcement Friday "has not calmed the anger, we need to go further", said FNSEA President Arnaud Rousseau.
"We have a government that doesn't care about its farmers," said Lucie Delbarre, general secretary of the Pas-de-Calais FDSEA branch.
"As you can see, it's a pressure cooker ready to explode."
The demonstrators have also attacked free trade agreements between the European Union and food exporters, especially a deal with the South American bloc Mercosur that is still in the works.
But farmers appeared to be divided over whether Attal's concessions were enough.
Farmers across France, the European Union's leading agricultural power, have expressed a mixture of anger and despair.
One group of protesters hung an effigy of a farmer in overalls from a mock gallows by the A10 motorway west of Paris.
As the unions made their announcement, Attal's office said the prime minister would visit a cattle farm in the western France region of Indre-et-Loire on Sunday morning.
The government has been trying to keep discontent among farmers from spreading just months ahead of European Parliament elections, which are seen as a key test for President Emmanuel Macron's government.
Francois Ruffin, a lawmaker with the left-wing France Unbowed (LFI) party, said the government needed to "set a course for French agriculture.
"We need to tell it what it should be doing: is its aim to compete with factory farms in Brazil or Ukraine, or is its aim to feed the French properly?" he added.
