India, Jan. 14 -- French farmers steered some 350 tractors on Tuesday over cobbles-toned Paris avenues toward Parliament to protest low incomes and an EU trade deal with South America that they fear threatens their livelihoods. Escorted by police, the tractors tangled rush-hour traffic as they rumbled down the Champs-Elysees and other Parisian avenues, and then over the Seine River to reach the National Assembly.

Farmer anger in France and other European countries has escalated over a rash of challenges recently. The unions leading Tuesday's protests said they are demanding concrete and immediate action to defend France's food security.

French farmers say their earnings are being squeezed by rising costs for fuel, fertiliser, and animal...