AMSTERDAM - Dutch farmers and construction workers blocked roads with tractors on Wednesday and gathered outside the offices of national broadcaster NOS in the latest of a series of protests over environmental pollution rules.

The protests began after a court ruling in May found the Netherlands in violation of EU rules on "reactive nitrogen" pollution, sparking a political debate over how to respond.

Farms are a major source of excess nitrogen, along with the construction and transport industries, and farmers feel they are being unfairly singled out.

Convoys of tractors and scattered demonstrations disrupted rush hour traffic on major motorways across the country.

One tractor carried a banner saying "no farmers, no food", echoing their central argument.

Dozens of tractors gathered outside the "media park" in the city of Hilversum, the country's main broadcasting hub. Farmers are "written off" in the media as useless and dependent on subsidies, said one unidentified spokesman.

"We're not looking for more money or a better contract, but for more respect and fewer rules," he said.

The Dutch Senate passed a law Tuesday night containing emergency measures to tackle the nitrogen problem, including a measure that will lower the speed limit to 100 kph nationwide from March.

Other protests on Wednesday took place on highways, in The Hague, and near a Shell refinery in Rotterdam.