NAVALMORAL DE LA MATA, Spain (AP) — Farmers in fluorescent yellow vests have begun blocking highways in southwestern Spain with tractors and other vehicles in the latest mass protest over what they say are plummeting incomes for agricultural workers.

The rallies Tuesday, predominantly in the Extremadura region that borders Portugal, were called by several labor unions to demand government action to ensure more realistic retail prices for fruit and vegetables.

Ángel García, head of the regional young farmers association Asaja, urged all farm workers in Extremadura to strike. He said about 700 tractors would join the road blockages.

The almost daily protests across Spain against high production costs and low prices for farm produce pose a tough challenge for the country's month-old Socialist-led coalition government as the European Union plans to cut agricultural subsidies. The protests also come amid tariff threats by the U.S.

The unions and the government also blame major supermarket chains for slashing prices on fruit and vegetables and forcing farmers to sell their goods for less.