Thousands of farmers and other anti-establishment demonstrators protested Saturday in a park in The Hague against Dutch government plans to reduce nitrate emissions, while elsewhere in the city climate activists angry at what they call state support for the fossil fuel industry broke through police lines to block a major road. The simultaneous demonstrations — a few kilometers (miles) from one another — come days before Dutch voters go to the polls in provincial elections Wednesday that indirectly also elect the national parliament’s upper house and could have an effect on proposals for reducing nitrate pollution. Police said they stopped an unknown number of tractors that were headed for the farmers' demonstration. The municipality banned all but two “symbolic” tractors from participating, citing safety concerns. As thousands of people, many carrying the upside-down Dutch flags that have become synonymous with farmers' protests and balloons emblazoned with the logo of the far-right Forum for Democracy party, gathered peacefully in front of a stage for the demonstration, the two permitted tractors drove slowly across the park. Earlier, Rotterdam broadcaster Rijnmond showed video of a convoy of tractors crossing the city’s Erasmus Bridge early Saturday, apparently on their way to The Hague. One of the tractors was emblazoned with a banner saying in Dutch “#proudofthefarmer.” As the farmers were gathering in a park in the south of the city, Mayor Jan van Zanen gave police permission to use a water cannon on Extinction Rebellion protesters who blocked a major highway in the downtown area near where it runs past the temporary home of the Dutch parliament. Police said demonstrators who refuse to leave the road would be detained. The highway was blocked in both directions, but police did not immediately use the water cannon. The twin demonstrations prompted authorities to place army trucks near some crossroads ready to block the streets if tractors or other protest vehicles tried to drive into the city center. Anger at moves to cut nitrate emissions have spread from the Netherlands to other European nations. Just over a week ago, farmers drove hundreds of tractors into the heart of the Belgian capital, Brussels, snarling traffic. At protests in recent years, farmers have driven hundreds of tractors into the center of The Hague and also used them to blockade supermarket warehouses. The government has said that nitrate emissions, which are produced by livestock, transport and industry, must be drastically reduced close to nature areas that are part of a network of protected habitats for endangered plants and wildlife stretching across the 27-nation European Union. The coalition wants to cut emissions of pollutants, predominantly nitrates, by 50% nationwide by 2030. Ministers call the proposal an “unavoidable transition” that aims to improve air, land and water quality, and have warned that it will mean "that not all farmers can continue their business.”