THE HAGUE, Netherlands (AP) — Cars crashed into tires and other garbage piled on a highway in the northern Netherlands in the early hours of Thursday, police said, as protests by radical farmers against government plans to rein in nitrogen emissions continued.

Prime Minister Mark Rutte branded the protests “unacceptable.”

Police in the northern province of Friesland said nobody was injured when several cars were involved in an accident caused by dumped garbage, but warned motorists to be alert to “extremely dangerous situations” caused by the farmers' protest actions.

A handful of new protests took place overnight, including farmers burning hay bales near a major highway, despite police and security authorities appealing to farmers Wednesday to halt the dumping.

“Protesting is a fundamental right and as long as it stays within the limits of the law, a lot is possible,” the emergency services said in a joint statement. But they said the latest actions “seriously endanger road safety and can lead to life-threatening situations for road users.”

In a sign of the increasingly radicalized farmer protests, cleanup operations have been hampered by intimidation of contractors hired to clear roads and by the presence of asbestos in some of the piles of debris dumped on roads.

“Wilfully endangering others, damaging our infrastructure and threatening people who help clean up is beyond all limits,” Rutte said in a tweet.

“These life-threatening actions must stop. There are plenty of other ways to express your dissatisfaction within the law. Most farmers do that,” he added.

The farmers are angry at government targets for reining in emissions of nitrogen oxide and ammonia that they say threaten to decimate the farming industry and their way of life.

The ruling coalition wants to cut emissions of pollutants by 50% nationwide by 2030 to improve soil, air and water quality in an EU nation known for its intensive farming practices. It has called on provincial authorities to draw up plans to reduce emissions and earmarked an extra 24.3 billion euros ($24.6 billion) to fund the changes.