Farmers have clashed with police in Belgium, spraying officers with liquid manure and setting fire to piles of tyres in a fresh show of force as European Union agriculture ministers met in search of ways to address their concerns.

Brussels police said that 900 tractors had entered the city of Brussels, many bearing down on the European Council building where the ministers were meeting.

Smoke drifted through the air near where police in riot gear used water cannons to defend the EU’s headquarters from behind concrete barriers and barbed wire.

The farmers are protesting against red tape and competition from cheap imports from countries where the EU’s relatively high standards do not have to be met. They lined up scores of tractors down main roads leading to the city’s European Quarter, snarling traffic and blocking public transport.

A few tractors forced their way through one barrier, sending officers scurrying.

Some are lamenting what they see as the slow death of working the land. “Agriculture. As a child you dream of it, as an adult you die of it,” said one.

At the start of the month, a similar demonstration turned violent as farmers torched hay bales and threw eggs and firecrackers at police near a summit of EU leaders.

The protests are the latest in a series of rallies and demonstrations by farmers across Europe.

On Saturday, French President Emmanuel Macron was greeted with boos and whistles at the opening of the Paris Agricultural Show by farmers who claim that he’s not doing enough to support them. Spain, the Netherlands and Bulgaria have been hit by protests in recent weeks.

The movement has gathered pace as political parties campaign for Europe-wide elections on June 6-9. It’s already had results. Earlier this month, the EU’s executive branch shelved an anti-pesticide proposal in a concession to the farmers, who comprise an important voting constituency.

On the other side of the barriers in Brussels, the ministers were keen to show they’re listening.

The EU presidency, currently held by Belgium, acknowledged that the farmers’ concerns include the burden of respecting environmental policies, a drop in assistance from the bloc’s agricultural subsidy system and the impact of Russia’s attacks on Ukraine’s grain supplies.

“We hear, clearly, their complaints,” said David Clarinval, Belgium’s agriculture minister. Still, he urged the protesters to refrain from violence. “We can understand that some are in difficult circumstances, but aggression has never been a source for solutions.”